Firefox 70 Platform Layout Release Notes

Noteworthy Changes

Features

• Implement support for the multi-keyword syntax for the `display` property (bug 1038294)
• Ship support for `text-decoration-thickness`, `text-underline-offset`, `text-decoration-skip-ink` (bug 1555865, bug 1573724, bug 1572800)
• Improve contrast of link colors in high-contrast mode (bug 697836)

All Bugs Fixed

CSS Parsing and Computation

bug 782551 Drop dd text-indent quirk

bug 1038294 [css-display] Implement the multi-keyword syntax for the 'display' property

bug 1105868 Support 'display: inline list-item' and 'display: inline flow-root list-item'

bug 1291187 getComputedStyle() of "flex-basis" should return "10%" if the style sets to "calc(0px + 10%)"

bug 1339672 [css-grid] grid-auto-columns/rows should accept multiple track-size values

bug 1404140 Consider flushing layout in a more fine-grained way in getComputedStyle.

bug 1421938 Quotes marks in tag are not localized when using lang attribute

bug 1480146 Can we do some sort of sharing across <style> in different instantiations of a shadow DOM component?

bug 1487493 Enable pref for CSS Containment (layout.css.contain.enabled)

bug 1526447 Remove NS_STYLE_GRID_REPEAT macro definitions

bug 1533569 freeze UA sheet shared memory and enable the feature

bug 1549872 Intermittent /css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-contain-png-001p.html | Testing http://*/object-fit-contain-png-001p.html == http://*/mozilla-central-reftests/images3/object-fit-contain-png-001-ref.html

bug 1553545 [css-fonts] font-size:xxx-large

bug 1554342 Perma [tier 2] /css/css-contain/contain-layout-baseline-005.html | Testing http://web-platform.test:8000/css/css-contain/contain-layout-baseline-005.html == http://web-platform.test:8000/css/css-contain/reference/contain-layout-baseline-005-ref.html

bug 1555865 adding support for text-decoration subproperty text-decoration-width (or rather, text-decoration-thickness) in the style system

bug 1556282 Reliably-failing /css/css-contain/contain-layout-button-001.html | Testing http://web-platform.test:8000/css/css-contain/contain-layout-button-001.html == http://web-platform.test:8000/css/css-contain/reference/contain-layout-button-001-ref.html

bug 1558929 adding from-font support to the style system

bug 1559276 Retiring support for 3-valued <position> (excluding background)

bug 1562086 [fill-stroke] [filter-effects] [css-color] percentage opacity

bug 1563892 We incorrectly allow to create a percentage token with CSS variables.

bug 1564085 Sync servo stuff.

bug 1564597 ignore differences in inherited, pref-controlled properties for cached scrollbar style assertions

bug 1565064 Remove plain_text.wrap_long_lines prefs from firefox.js and mobile.js

bug 1565214 Centralize property restrictions for pseudo-elements, and don't apply it for UA sheets.

bug 1565562 [media-queries][css-sizing] Support <number> (and therefore calc) as a <ratio>

bug 1567108 display table and outline does not work together; needs a DOMRefresh.

bug 1567282 Rename text-decoration-width to text-decoration-thickness, to match compat & current spec

bug 1567333 Remove the ability to build the style crate without bindgen.

bug 1567349 Background-position-y parsing WPT is bogus.

bug 1568083 Sync servo stuff.

bug 1568446 Cherry-pick servo/servo#23824

bug 1569505 Intermittent /css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-contain-png-001i.html | Testing http://web-platform.test:8000/css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-contain-png-001i.html ==

bug 1569648 Assertion failure: false (MOZ_ASSERT_UNREACHABLE: an StyleFilter of type URL should have a non-null URL), at /builds/worker/workspace/build/src/layout/svg/nsSVGFilterInstance.cpp:142

bug 1569825 Unexpose some old 'display' values in devtools

bug 1569911 Sync servo stuff.

bug 1570096 Fix parsing of align=bottom on replaced elements.

bug 1571151 Simplify SVGPathData parser.

bug 1571278 Intermittent /css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-scale-down-png-002c.html | Testing http://web-platform.test:8000/css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-scale-down-png-002c.html == http:/

bug 1571335 Perma tier2 windows10-aarch64 /css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-cover-png-002c.html | Testing http://web-platform.test:8000/css/vendor-imports/mozilla/mozilla-central-reftests/images3/object-fit-cover-png-002c.html

bug 1571537 Do not write manual glue code for the order property.

bug 1572252 running Firefox with RUST_LOG="debug" results in a null pointer deref

bug 1572288 mark wpt versions of variable-font-face tests as needing ahem pref setting

bug 1572303 Update text-underline-offset so it applies to :first-line / ::first-letter / ::placeholder

bug 1572304 Update text-decoration-skip-ink so it applies to :first-line / ::first-letter / ::placeholder

bug 1572738 Font-size is computed incorrectly for a collection of child elements that use mixed font families, when their shared parent sets a font-size using CSS calc that mixes vw and em units.

bug 1572805 Use cbindgen for text-emphasis-style

bug 1573106 Use shortest serialization consistently for text-emphasis-style

bug 1573974 Add back newly-valid `text-decoration` values in text-decoration-valid.html

bug 1574148 Sync servo stuff.

bug 1574179 Simplify <img align> rules in quirks.css

bug 1574306 Intermittent /css/css-flexbox/auto-margins-001.html | Testing http://web-platform.test:8000/css/css-flexbox/auto-margins-001.html == http://web-platform.test:8000/css/css-flexbox/auto-margins-001-ref.html

bug 1575062 Add use counters for unimplemented CSS properties

bug 1575559 Make font-variant-alternates use cbindgen.

bug 1575560 contain:size shouldn't apply to inline-table boxes

bug 1575608 Some miscellaneous CSS property cleanups

bug 1575713 Some followup font-feature-values / font-variant-alternates cleanups

bug 1576194 Remove kDisplayKTable.

bug 1576229 Dynamic changes due to rules in user sheets don't get applied in Shadow DOM

bug 1576587 Rustfmt declaration_block.rs and glue.rs

bug 1576666 use cbindgen for clip / -moz-image-region

bug 1576703 Update cbindgen.

bug 1577389 nsStyleMargin::GetMargin and nsStylePadding::GetPadding are a bit slow

bug 1577592 Shadow Parts seem to not match ::part when a document fragment with [part] elements inside of it is imported into a shadow root

CSS Transitions and Animations

bug 1559231 [motion-1] Support offset-anchor

bug 1564366 CSS animation on :before element not unset

bug 1568370 [motion-1] Incorrect motion path on SVG layout when transform-box is fill-box

bug 1569795 [motion-1] Motion path is overridden when we have transform animations

DOM: CSS Object Model

bug 1360475 Use Union instead of Overload for DOMMatrix/DOMMatrixReadOnly Constructors

bug 1364875 Align DOMMatrix stringifier with the spec

bug 1541861 CSSStyleSheet.prototype.deleteRule confusing error message

bug 1566684 Assertion failure: cache->GetWrapperMaybeDead() == obj, at src/obj-firefox/dist/include/mozilla/dom/BindingUtils.h:1389

bug 1567053 Make default ::-moz-focus-inner border color more accessible

Layout

bug 697836 Contrast between links and background is very low in high contrast mode on Windows

bug 1300293 reflowing view-source very slow in nsLineBox::RFindLineContaining

bug 1351924 Use nsChangeHint_UpdateComputedBSize to properly set the IsBResize() flag on reflow input

bug 1367830 mark hidden window as inactive (so we will soon not run the refresh driver in the hidden window)

bug 1420528 floated element is missing, after column-break in multicol

bug 1468654 Firefox 60.0.2 not rendering columns in list correctly

bug 1472546 Moving position:absolute elements performance far worse (i.e. terrible) with vertical-rl pages than vertical-lr pages

bug 1482938 Container height does not recalculate if add content to the container dynamically and after timeout set height auto to the base container

bug 1516322 MobileViewportManager::ShrinkToDisplaySizeIfNeeded() is broken in RDM on Windows with non WebRender

bug 1520096 Enable reftests introduced in bug 1423013 on WebRender

bug 1541229 Consider to tweak idle detection during page load

bug 1553012 Need a way to do PresShell::ScrollFrameRectIntoView across document boundaries for 'Find in page'

bug 1555142 Assertion failure: false (MOZ_ASSERT_UNREACHABLE: expected to find a line with HasLineClampEllipsis), at src/layout/generic/nsBlockFrame.cpp:1179

bug 1557857 Adding web-platform tests ref-tests for text-underline-offset

bug 1560188 Some display items are reported as frames in memory reports.

bug 1561450 Scrolling to the bottom on phoronix.com locks up scrolling

bug 1561657 update text-underline-offset to meet resolved CSS spec issue 4021

bug 1562503 Use nsPresShell::IsRootContentDocumentCrossProcess to tell whether we need to create MobileViewportManager or ZoomConstraintsClient

bug 1562701 Rework the reframing logic for `<details>` elements

bug 1562704 Fix text-underline-offset for japanese text

bug 1563059 contain-paint-clip-015.html and -016.html need a fuzzy annotation instead of a failure annotation

bug 1563278 web-platform-test contain-paint-008.html fails on mac & windows due to having "PASS" text mis-positioned by < 1px

bug 1564021 Treat viewport meta tag as an empty tag if there is no valid content

bug 1564555 Enable some more ESLint rules for layout/

bug 1564788 Dereference after null check in PrintPreviewUserEventSuppressor::HandleEvent(Event*)

bug 1565109 Tier 2 Reftest on android-hw-p2-8 <random> application crashed [@ <webrender_bindings::moz2d_renderer::Moz2dBlobImageHandler as webrender_api::image::BlobImageHandler>::prepare_resources]

bug 1565129 plain_text.wrap_long_lines no longer working as before

bug 1565136 Split WipeContainingBlock to save work for those checks requiring no frame construction items

bug 1565965 Layout Debugger fails to load documents

bug 1566215 Consider switching the layout debugger to use e10s

bug 1567328 improve the keyboard shortcuts in the Layout Debugger

bug 1567397 Permafailing tier 2 TEST-UNEXPECTED-PASS | bugs/1562733-rotated-nastaliq-1.html == bugs/1562733-rotated-nastaliq-1-ref.html | image comparison, max difference: 253, number of differing pixels: 1392

bug 1567643 add text-decoration-skip-ink to web platform tests using text-decorations

bug 1567818 Forward declare nsLayoutPhase

bug 1567982 The "reload" button on the layout debugger's toolbar is broken

bug 1568051 JS-implemented nsIContentPolicy can be interrupted during frame construction

bug 1568107 Add telemetry to nsRefreshDisplay::Tick

bug 1568124 Fix dynamic change handling of layout.css.dpi and layout.css.devPixelsPerPx prefs

bug 1568536 Don't propagate viewport styles for boxless elements.

bug 1568542 Intermittent bugs/1562733-rotated-nastaliq-2.html == bugs/1562733-rotated-nastaliq-2-ref.html | image comparison, max difference: 93, number of differing pixels: 16

bug 1569060 show process IDs in the layout debugger

bug 1569077 add some Layout Debugger features to help with command line scripting

bug 1569084 update command line help to use two-dash form of --layoutdebug

bug 1569263 Remove/revert .ini files for now-passing `object-fit` WPT tests

bug 1569345 Some object-fit WPT tests need a fuzzy annotation (rather than fails)

bug 1570520 Intermittent Tier 2 Android 8 text-stroke/webkit-text-stroke-property-X.html == text-stroke/webkit-text-stroke-property-X-ref.html | image comparison, max difference: Y, number of differing pixels: Z

bug 1570550 Frequent text-stroke/webkit-text-stroke-property-X.html == text-stroke/webkit-text-stroke-property-X-ref.html | image comparison, max difference: X, number of differing pixels: Y

bug 1570721 Add an API to emulate dark mode from devtools.

bug 1570726 Move frame state bits carrying from nsCSSFrameConstructor::CreateContinuingFrame() into nsFrame::Init()

bug 1570759 Consider enabling the optimization to not flush when getting fixed margins from getComputedStyle().

bug 1571118 Keep NS_FRAME_FIRST_REFLOW bit in nsBlockFrame::Reflow() a bit longer

bug 1571250 convert flags passed to ReflowChild/FinishReflowChild/etc. to an enum class

bug 1571612 Collect Style/Layout Flush Requests per Flush and Flushes per Tick

bug 1571855 Disable warning for Is##name_##Frame() in Clang

bug 1572114 shape-image code can request reflow from reflow if the shape image is complete.

bug 1572291 add support for vertical writing modes to text-decoration-skip-ink

bug 1572502 Delete the in-tree layout/generic/{FrameIdList.h, FrameTypeList.h}

bug 1572589 update skip-ink to scale down line padding with the thickness of the decoration line

bug 1572779 Permafail tier2 TEST-UNEXPECTED-PASS | async-scrolling/perspective-scrolling-1.html == async-scrolling/perspective-scrolling-1-ref.html | image comparison, max difference: 0, number of differing pixels: 0

bug 1573218 fix scaling for padding between text for text-decoration-skip-ink

bug 1573242 fixing scaling for line thickness padding in text-decoration-skip-ink

bug 1573922 add more reftests for text-decoration-skip-ink

bug 1574016 patch from bug 1547277 contains logic error

bug 1574107 Remove nsIFrame::IsBlockInside since it's dead code

bug 1574310 run clang-format on layout

bug 1574447 Remove workaround for bug 1574225.

bug 1574544 crash near null in [@ nsCSSFrameConstructor::IsValidSibling]

bug 1574994 Remove display:-moz-inline-grid and -moz-inline-stack

bug 1575377 Remove BlockReflowInput::mHasUnconstrainedBSize

bug 1575694 Short circuiting the refresh driver in WebVR immersive mode on Android break the MediaRecorder

bug 1575806 Minor cleanup of the preference stylesheet code.

bug 1576018 tweak frame debugging output

bug 1577745 Remove dead version of nsStyleDisplay::IsOriginalDisplayInlineOutside.

Layout: Block and Inline

bug 1558849 Intermittent /css/vendor-imports/mozilla/mozilla-central-reftests/ruby/ruby-inlinize-blocks-002.html

bug 1565037 More refactor and cleanup for nsBlockFrame::ComputeFinalBSize()

bug 1566945 pass line box through from nsTextFrame::SetLength to nsBlockFrame::AddFrames

bug 1567036 nsBidiPresUtils line iterator can get off due to mPrevFrame being out of sync due to ResolveParagraphWithinBlock

bug 1567098 img tag within p tags not separated by a space from the text is not rendered correctly

bug 1573907 list item with value attribute in <ol reversed> causes the list to start too high (by one per item with value)

bug 1574552 Assertion failure: aFloat->GetParent()->FirstContinuation() == mBlock->FirstContinuation(), at src/layout/generic/BlockReflowInput.cpp:541

Layout: Columns

bug 1506293 crash near null in [@ nsContainerFrame::ReflowOverflowContainerChildren]

bug 1547391 Assertion failure: isSingleInsert || frameType != LayoutFrameType::Details, at src/layout/base/nsCSSFrameConstructor.cpp:7089

bug 1548100 Fix the height of column rules after enabling column-span

bug 1564649 multicol reflow doesn't dirty enough when being reflowed without any dirty bits

bug 1565665 enabling column-span pref shifts the baseline (?) of an inline-block multicolumn

bug 1566672 use-after-poison in [@ nsCSSFrameConstructor::MaybeRecreateContainerForFrameRemoval]

bug 1568001 Assertion failure: found (not in child list), at src/layout/base/nsLayoutUtils.cpp:1465

bug 1569252 Move HasColumnSpanSiblings boolean property into nsIFrame

bug 1569701 Use GetEffectiveComputedBSize() when applying ColumnSetWrapper's block-size constraint for ColumnSet

bug 1571849 Assertion failure: aReflowInput.AvailableBSize() != nscoord((1 << 30) - 1) (Available block-size should be constrained because it's restricted by the computed block-size when our reflow input is created in nsBlockFrame::ReflowBlockFrame()!)

bug 1571897 Assertion failure: childReflowStatus.IsComplete() (We gave flex item unconstrained available height, so it should be complete), at src/layout/generic/nsFlexContainerFrame.cpp:1815

bug 1571930 Convert MOZ_ASSERT in nsColumnSetFrame::ReflowChildren() to be non-fatal

bug 1572912 Enable column-span preference in individual tests to fix more existing failures

bug 1573329 Nested column is not balancing correctly when column-span is enabled

bug 1573761 Add a web-platform reftest multicol-breaking-nobackground-004.html

bug 1575106 Nested columns can create zero height column-boxes indefinitely if the content's block-size is larger than the column container

bug 1575305 Some ColumnSet clean up

Layout: Floats

bug 1568615 [css-shapes] Accept percentage for shape-image-threshold

bug 1571135 Remove the preference to control breaking floats inside columns

Layout: Form Controls

bug 1418061 In the new FF57 date input widget with pt locale days of the week appear as segunda, terça, quarta,... These are too long and appear superimposed and scroll bars show up.

bug 1450173 input with date/time type doesn't center its contents, with "text-align:center"

bug 1457628 File input "Browse" button is vertically squished when given style "height: calc(.....)" due to block-size: inherit in forms.css

bug 1481112 User Agent Stylesheet Default for select, button

bug 1561787 readonly date input shows active clear x

bug 1561882 'change' event not triggering after some action in 'input' event handler

bug 1567191 Datetime input attribute value changes is not correct

bug 1569078 Textarea won't resize properly in translate.google.com

bug 1571222 Permafail css-ui-invalid/select/select-disabled-fieldset-1.html == css-ui-invalid/select/select-fieldset-ref.html | image comparison, max difference: 9, number of differing pixels: 1

bug 1571764 When line-height is applied to select, the element ends up being slightly (~2px?) taller than expected

bug 1573999 Perma fail css-ui-invalid/select/select-disabled-fieldset-2.html == css-ui-invalid/select/select-fieldset-ref.html | image comparison, max difference: 9, number of differing pixels: 1

Layout: Generated Content, Lists, and Counters

bug 1567773 Lists in contenteditable

bug 1574060 Implement layout for 'display: flow-root list-item'

bug 1574123 Crash in [@ nsContainerFrame::GetSpokenMarkerText]

bug 1576821 [css-lists-3] counter(name, none) should be invalid

Layout: Grid

bug 1576355 css grid position incorrect after class name change

Layout: Images, Video, and HTML Frames

bug 1522288 Should we start image load using microtask and not Gecko's current stable state (== end-of-task)?

bug 1554777 Intermittent Tier 2 /css/css-backgrounds/border-image-width-006.xht | Testing http://web-platform.test:8000/css/css-backgrounds/border-image-width-006.xht == http://web-platform.test:8000/css/reference/ref-filled-green-100px-square.xht

bug 1565384 object-fit for <embed> and <object> is unreliable when running over http

bug 1565690 Prefer image aspect ratio to inferred aspect ratio.

Layout: Positioned

bug 1456358 Inhibit RecomputePosition optimization when absolute pos elements depend upon placeholder pos.

Layout: Ruby

bug 1557825 [css-display] Implement 'display: block ruby'

Layout: Scrolling and Overflow

bug 1566991 Add some assertions to validate that mobile viewport zoom factors are positive

bug 1567237 overflow:scroll on elements not needing to scroll prevents keyboard panning on main document, unlike Chrome

bug 1568673 Add a few more assertions to validate that mobile viewport zoom factors are positive

bug 1568778 StickyTableHeaders still doesn't work correctly even after bug 1543599.

Layout: Tables

bug 1547759 mis-positioned row background in a position: relative table cell with RTL direction

bug 1563050 [css-contain] layout containment should suppress baseline alignment for table-cell

bug 1564308 {inc}visibility:collapse code makes some adjustments multiple times when the insides of a table aren't reflowed

bug 1571249 remove BCTableCell as a distinct LayoutFrameType

bug 1571517 Whitespace-only table cell breaks copy to clipboard

bug 1577364 Remove NS_TABLE_CELL_HAS_PCT_OVER_BSIZE frame bit since it's not used

Layout: Text and Fonts

bug 1437367 Remove the layout.css.paint-order.enabled pref

bug 1513423 make gfxFont::Measure always lay out glyphs left to right

bug 1554208 Implement FT2 backend for the cross-process shared font list

bug 1559044 text blinks while page loading

bug 1565966 Issues with selecting the Franklin Gothic (Medium) font on Windows using the shared font list [was: The Segoe UI Bold font will fallback to Arial Regular after two minutes of running the browser]

bug 1566333 Crash in [@ mozilla::ipc::MessageChannel::Send | mozilla::dom::PContentChild::SendInitializeFamily]

bug 1567437 Add memory reporting for hyphenation resources

bug 1567752 Crash in [@ mozilla::dom::FontFaceSet::OnFontFaceStatusChanged]

bug 1568501 talos regression on perf-reftest-singletons/bidi-resolution-1.html or (on ARM64 Windows) Perma [tier2] console.error: "You should not call finishTest without having first initted the Profiler" (from perf-reftest-singleton suite timing out)

bug 1568514 Add telemetry to report memory usage for auto-hyphenation

bug 1572800 Enable "text-decoration-skip-ink" by default on Nightly/early-beta

bug 1573229 Make memory allocation functions in HyphenReporter infallible, as assumed by libhyphen

bug 1573249 text-decoration-skip-ink doesn't look good on Japanese (Chinese) sentences

bug 1573724 pref text-underline-offset on in Nightly/early-beta

bug 1573725 pref text-decoration-thickness on by default in Nightly/early-beta

bug 1574031 Intermittent text-decoration/decoration-style-standards.html == text-decoration/decoration-style-standards-ref.html | image comparison, max difference: 255, number of differing pixels: 9

bug 1574066 Intermittent /css/css-text-decor/text-decoration-color.html | Testing http://web-platform.test:8000/css/css-text-decor/text-decoration-color.html == http://web-platform.test:8000/css/css-text-decor/reference/text-decoration-color-ref.html

bug 1574392 Crash in [@ SkTextBlob::getIntercepts]

bug 1574927 skip-ink is incorrect for sideways (e.g. Latin) text in vertical writing modes after an upright (e.g. CJK) run

bug 1575315 FF appears frozen while examining fonts loading smile.amazon.com (looking for codepoint U+FFFE)

bug 1575338 Underlines intermittently render without ink-skipping, during reftest runs

bug 1575908 Assertion failure: mJustificationSpacings.IsEmpty(), at /builds/worker/workspace/build/src/layout/generic/nsTextFrame.cpp:3833

bug 1576356 micro-optimize skip-ink rendering by using an autoarray for intercepts

bug 1576553 stroked text with ligature painted incorrectly when selection intersects ligature

bug 1576846 Crash in [@ mozilla::fontlist::FontList::Alloc]

bug 1576972 Assertion failure: hasNext (Can't find frame in lines!), at /builds/worker/workspace/build/src/layout/base/nsBidiPresUtils.cpp:255

bug 1577053 Debian 10 - layout/reftests/w3c-css/submitted/text-decor-3/reftest.list | image comparison, max difference: 200, number of differing pixels: 64 | multiple failures

Print Preview

bug 1406291 [Layout] floating table following quickly after page-break-after style is not printed

Printing: Output

bug 1404868 float following page-break-after disappears in print layout

bug 1406050 non-floating table doesn't show up after page-break-after

bug 1565932 Crash in [@ shutdownhang | NtUserGetMessage | NtUserGetMessage | NtUserGetMessage | WaitForCompletionMessage | PrintUIDocumentPropertiesWrap]

Printing: Setup

bug 1565274 nsPageSequenceFrame.h includes itself

SVG

bug 1353164 dominant-baseline will become inherited in SVG 2 (and CSS Inline 3)

bug 1514538 SVGMatrix and DOMMatrix are not interchangeable in Path2D.addPath

bug 1555851 Assertion failure: tmpDist >= 0.0f (distance values must be non-negative), at src/dom/smil/SMILAnimationFunction.cpp:584

bug 1561721 remove color-rendering tests

bug 1564208 Setting `svg.disabled` to `true` causes extension icons to disappear

bug 1566697 Build error in SVGPathData.cpp:170:10: error: use of undeclared identifier 'isfinite'

bug 1567962 Remove "Content used context-fill-opacity when not in a context element" warning

bug 1569474 dispatch cut, copy and paste events to SVG graphics elements

bug 1572904 crash near null in [@ mozilla::dom::SVGElement::FlushAnimations]

bug 1572967 Intermittent TEST-UNEXPECTED-TIMEOUT | /svg/animations/scripted/onhover-syncbases.html | Check if onhover events reset correctly when triggred multiple times - Test timed out

bug 1573364 Convert VarCache prefs in layout/svg/ to static prefs