[css-contain] "will-change: contain" should create a stacking context

There was a Mozilla test failing in Chromium
because of "will-change: contain" is not creating a stacking context.

This has been clarified in the following CSSWG issue:
https://github.com/w3c/csswg-drafts/issues/4612

The fix is just adding the "contain" property
to HasPropertyThatCreatesStackingContext() in computed_style.cc.

BUG=881057
TEST=css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001b.html

Change-Id: I52a50cfac7bc46a74557760006dc46abba0632ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975913Reviewed-by: Oriol Brufau <obrufau@igalia.com>
Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726569}

third_party/blink/renderer/core/style/computed_style.cc

@@ -1017,6 +1017,7 @@ static bool HasPropertyThatCreatesStackingContext(
       case CSSPropertyID::kPosition:
       case CSSPropertyID::kMixBlendMode:
       case CSSPropertyID::kIsolation:
+      case CSSPropertyID::kContain:
         return true;
       default:
         break;

third_party/blink/web_tests/TestExpectations

@@ -590,7 +590,6 @@ crbug.com/881057 [ Mac ] external/wpt/css/vendor-imports/mozilla/mozilla-central
 crbug.com/881057 [ Mac ] external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html [ Failure ]
 crbug.com/881057 [ Mac ] external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html [ Failure ]
 crbug.com/880802 external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html [ Failure ]
-crbug.com/881057 external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001b.html [ Failure ]
 
 crbug.com/880802 virtual/layout_ng_fieldset/external/wpt/css/css-contain/contain-layout-017.html [ Failure ]
 crbug.com/626703 virtual/layout_ng_fieldset/external/wpt/css/css-contain/contain-layout-breaks-002.html [ Failure ]
@@ -615,7 +614,6 @@ crbug.com/881057 [ Mac ] virtual/layout_ng_fieldset/external/wpt/css/vendor-impo
 crbug.com/881057 [ Mac ] virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-004.html [ Failure ]
 crbug.com/881057 [ Mac ] virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-clip-005.html [ Failure ]
 crbug.com/880802 virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-ignored-cases-ruby-stacking-and-clipping-001.html [ Failure ]
-crbug.com/881057 virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-paint-stacking-context-001b.html [ Failure ]
 crbug.com/965491 virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-size-fieldset-002.html [ Failure ]
 crbug.com/845235 virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-size-flex-001.html [ Failure ]
 crbug.com/845235 virtual/layout_ng_fieldset/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/contain/contain-size-inline-flex-001.html [ Failure ]