Visited background-color alpha channel in Forced Colors Mode

Handle :visited background-colors in a similar way to the normal
background-color property in Forced Colors Mode.

Bug: 970285
Change-Id: I1dd0ac2530f3dec7de4b79de459d34e1d2ae193b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2393299Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Alison Maher <almaher@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#805825}

third_party/blink/renderer/core/css/resolver/style_cascade.cc

@@ -550,6 +550,8 @@ void StyleCascade::ForceColors() {
 
   int bg_color_alpha =
       style->VisitedDependentColor(GetCSSPropertyBackgroundColor()).Alpha();
+  int visited_bg_color_alpha =
+      style->ResolvedColor(style->InternalVisitedBackgroundColor()).Alpha();
   const SVGComputedStyle& svg_style = style->SvgStyle();
 
   MaybeForceColor(GetCSSPropertyColor(), style->GetColor());
@@ -604,6 +606,10 @@ void StyleCascade::ForceColors() {
   style->SetBackgroundColor(
       StyleColor(style->BackgroundColor().ResolveWithAlpha(
           style->GetCurrentColor(), WebColorScheme::kLight, bg_color_alpha)));
+  style->SetInternalVisitedBackgroundColor(
+      StyleColor(style->InternalVisitedBackgroundColor().ResolveWithAlpha(
+          style->GetCurrentColor(), WebColorScheme::kLight,
+          visited_bg_color_alpha)));
 }
 
 void StyleCascade::MaybeForceColor(const CSSProperty& property,
@@ -626,8 +632,10 @@ const CSSValue* StyleCascade::GetForcedColorValue(CSSPropertyName name) {
   CascadePriority* p = map_.Find(name, CascadeOrigin::kUserAgent);
   if (p)
     return ValueAt(match_result_, p->GetPosition());
-  if (name.Id() == CSSPropertyID::kBackgroundColor)
+  if (name.Id() == CSSPropertyID::kBackgroundColor ||
+      name.Id() == CSSPropertyID::kInternalVisitedBackgroundColor) {
     return CSSIdentifierValue::Create(CSSValueID::kCanvas);
+  }
   return cssvalue::CSSUnsetValue::Create();
 }
 

third_party/blink/renderer/core/css/resolver/style_cascade_test.cc

@@ -3530,4 +3530,29 @@ TEST_F(StyleCascadeTest, GetCascadedValuesInterpolated) {
   EXPECT_EQ("-5s", CssTextAt(map, "animation-delay"));
 }
 
+TEST_F(StyleCascadeTest, ForcedVisitedBackgroundColor) {
+  ScopedForcedColorsForTest scoped_feature(true);
+  ColorSchemeHelper color_scheme_helper(GetDocument());
+  color_scheme_helper.SetForcedColors(GetDocument(), ForcedColors::kActive);
+  UpdateAllLifecyclePhasesForTest();
+
+  TestCascade cascade(GetDocument());
+  cascade.State().Style()->SetInsideLink(EInsideLink::kInsideVisitedLink);
+  cascade.Add(ParseDeclarationBlock("background-color:#aabbccdd"),
+              CascadeOrigin::kAuthor, CSSSelector::kMatchVisited);
+  cascade.Apply();
+
+  Color forced_bg_color =
+      StyleColor(CSSValueID::kCanvas).Resolve(Color(), WebColorScheme::kLight);
+  Color expected_bg_color =
+      Color(forced_bg_color.Red(), forced_bg_color.Green(),
+            forced_bg_color.Blue(), 0xdd);
+
+  // Verify that the visited background color alpha channel is preserved in
+  // Forced Colors Mode.
+  EXPECT_EQ(
+      expected_bg_color,
+      cascade.State().Style()->InternalVisitedBackgroundColor().GetColor());
+}
+
 }  // namespace blink

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

@@ -2937,6 +2937,7 @@ class ComputedStyle : public ComputedStyleBase,
   FRIEND_TEST_ALL_PREFIXES(ComputedStyleTest, InitialVariableNames);
   FRIEND_TEST_ALL_PREFIXES(ComputedStyleTest,
                            InitialAndInheritedAndNonInheritedVariableNames);
+  FRIEND_TEST_ALL_PREFIXES(StyleCascadeTest, ForcedVisitedBackgroundColor);
 };
 
 inline bool ComputedStyle::HasAnyPseudoElementStyles() const {

third_party/blink/web_tests/external/wpt/forced-colors-mode/forced-colors-mode-40.html → third_party/blink/web_tests/external/wpt/forced-colors-mode/forced-colors-mode-39.html

@@ -2,7 +2,7 @@
 <meta charset="utf-8">
 <title>Forced colors mode - pseudo elements.</title>
 <link rel="help" href="https://www.w3.org/TR/css-color-adjust-1/#forced-colors-properties">
-<link rel=match href="forced-colors-mode-40-ref.html">
+<link rel=match href="forced-colors-mode-39-ref.html">
 <style>
   p::before {
     background: blue;