Delay loading the forced colors stylesheet

Due to memory regressions caused by loading the forced colors
stylesheet when the ForcedColors flag is enabled, delay loading
the stylesheet until forced colors is triggered for the first time.

Bug: 1167339
Change-Id: I6de0f02442dc5f1b23776daf2883fe4793293548
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633971
Commit-Queue: Alison Maher <almaher@microsoft.com>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845231}

third_party/blink/renderer/core/css/css_default_style_sheets.cc

@@ -89,20 +89,15 @@ static StyleSheetContents* ParseUASheet(const String& str) {
 
 CSSDefaultStyleSheets::CSSDefaultStyleSheets()
     : media_controls_style_sheet_loader_(nullptr) {
-  // Strict-mode rules.
-  String forced_colors_style_sheet =
-      RuntimeEnabledFeatures::ForcedColorsEnabled()
-          ? UncompressResourceAsASCIIString(IDR_UASTYLE_THEME_FORCED_COLORS_CSS)
-          : String();
   // Predefined @counter-style rules
   String predefined_counter_styles_sheet =
       RuntimeEnabledFeatures::CSSAtRuleCounterStyleEnabled()
           ? UncompressResourceAsASCIIString(
                 IDR_UASTYLE_PREDEFINED_COUNTER_STYLES_CSS)
           : String();
+  // Strict-mode rules.
   String default_rules = UncompressResourceAsASCIIString(IDR_UASTYLE_HTML_CSS) +
                          LayoutTheme::GetTheme().ExtraDefaultStyleSheet() +
-                         forced_colors_style_sheet +
                          predefined_counter_styles_sheet;
 
   default_style_sheet_ = ParseUASheet(default_rules);
@@ -121,13 +116,11 @@ CSSDefaultStyleSheets::CSSDefaultStyleSheets()
   default_svg_style_->CompactRulesIfNeeded();
   default_quirks_style_->CompactRulesIfNeeded();
   default_print_style_->CompactRulesIfNeeded();
-  default_forced_color_style_->CompactRulesIfNeeded();
   DCHECK(default_style_->UniversalRules()->IsEmpty());
   DCHECK(default_mathml_style_->UniversalRules()->IsEmpty());
   DCHECK(default_svg_style_->UniversalRules()->IsEmpty());
   DCHECK(default_quirks_style_->UniversalRules()->IsEmpty());
   DCHECK(default_print_style_->UniversalRules()->IsEmpty());
-  DCHECK(default_forced_color_style_->UniversalRules()->IsEmpty());
 #endif
 }
 
@@ -140,6 +133,7 @@ void CSSDefaultStyleSheets::PrepareForLeakDetection() {
   mathml_style_sheet_.Clear();
   media_controls_style_sheet_.Clear();
   text_track_style_sheet_.Clear();
+  forced_colors_style_sheet_.Clear();
   fullscreen_style_sheet_.Clear();
   webxr_overlay_style_sheet_.Clear();
   marker_style_sheet_.Clear();
@@ -160,15 +154,13 @@ void CSSDefaultStyleSheets::InitializeDefaultStyles() {
   default_svg_style_ = MakeGarbageCollected<RuleSet>();
   default_quirks_style_ = MakeGarbageCollected<RuleSet>();
   default_print_style_ = MakeGarbageCollected<RuleSet>();
-  default_forced_color_style_ = MakeGarbageCollected<RuleSet>();
   default_media_controls_style_ = MakeGarbageCollected<RuleSet>();
+  default_forced_color_style_.Clear();
   default_pseudo_element_style_.Clear();
 
   default_style_->AddRulesFromSheet(DefaultStyleSheet(), ScreenEval());
   default_quirks_style_->AddRulesFromSheet(QuirksStyleSheet(), ScreenEval());
   default_print_style_->AddRulesFromSheet(DefaultStyleSheet(), PrintEval());
-  default_forced_color_style_->AddRulesFromSheet(DefaultStyleSheet(),
-                                                 ForcedColorsEval());
 }
 
 RuleSet* CSSDefaultStyleSheets::DefaultViewSourceStyle() {
@@ -226,8 +218,10 @@ bool CSSDefaultStyleSheets::EnsureDefaultStyleSheetsForElement(
         ParseUASheet(UncompressResourceAsASCIIString(IDR_UASTYLE_SVG_CSS));
     default_svg_style_->AddRulesFromSheet(SvgStyleSheet(), ScreenEval());
     default_print_style_->AddRulesFromSheet(SvgStyleSheet(), PrintEval());
-    default_forced_color_style_->AddRulesFromSheet(SvgStyleSheet(),
-                                                   ForcedColorsEval());
+    if (default_forced_color_style_) {
+      default_forced_color_style_->AddRulesFromSheet(SvgStyleSheet(),
+                                                     ForcedColorsEval());
+    }
     changed_default_style = true;
   }
 
@@ -253,8 +247,10 @@ bool CSSDefaultStyleSheets::EnsureDefaultStyleSheetsForElement(
                                                      ScreenEval());
     default_print_style_->AddRulesFromSheet(MediaControlsStyleSheet(),
                                             PrintEval());
-    default_forced_color_style_->AddRulesFromSheet(MediaControlsStyleSheet(),
-                                                   ForcedColorsEval());
+    if (default_forced_color_style_) {
+      default_forced_color_style_->AddRulesFromSheet(MediaControlsStyleSheet(),
+                                                     ForcedColorsEval());
+    }
     changed_default_style = true;
   }
 
@@ -331,8 +327,10 @@ bool CSSDefaultStyleSheets::EnsureDefaultStyleSheetForXrOverlay() {
   default_style_->AddRulesFromSheet(webxr_overlay_style_sheet_, ScreenEval());
   default_print_style_->AddRulesFromSheet(webxr_overlay_style_sheet_,
                                           PrintEval());
-  default_forced_color_style_->AddRulesFromSheet(webxr_overlay_style_sheet_,
-                                                 ForcedColorsEval());
+  if (default_forced_color_style_) {
+    default_forced_color_style_->AddRulesFromSheet(webxr_overlay_style_sheet_,
+                                                   ForcedColorsEval());
+  }
   return true;
 }
 
@@ -349,6 +347,38 @@ void CSSDefaultStyleSheets::EnsureDefaultStyleSheetForFullscreen() {
                                            ScreenEval());
 }
 
+bool CSSDefaultStyleSheets::EnsureDefaultStyleSheetForForcedColors() {
+  if (forced_colors_style_sheet_)
+    return false;
+
+  String forced_colors_rules =
+      RuntimeEnabledFeatures::ForcedColorsEnabled()
+          ? UncompressResourceAsASCIIString(IDR_UASTYLE_THEME_FORCED_COLORS_CSS)
+          : String();
+  forced_colors_style_sheet_ = ParseUASheet(forced_colors_rules);
+
+  if (!default_forced_color_style_)
+    default_forced_color_style_ = MakeGarbageCollected<RuleSet>();
+  default_forced_color_style_->AddRulesFromSheet(DefaultStyleSheet(),
+                                                 ForcedColorsEval());
+  default_forced_color_style_->AddRulesFromSheet(ForcedColorsStyleSheet(),
+                                                 ForcedColorsEval());
+  if (svg_style_sheet_) {
+    default_forced_color_style_->AddRulesFromSheet(SvgStyleSheet(),
+                                                   ForcedColorsEval());
+  }
+  if (media_controls_style_sheet_) {
+    default_forced_color_style_->AddRulesFromSheet(MediaControlsStyleSheet(),
+                                                   ForcedColorsEval());
+  }
+  if (webxr_overlay_style_sheet_) {
+    default_forced_color_style_->AddRulesFromSheet(webxr_overlay_style_sheet_,
+                                                   ForcedColorsEval());
+  }
+
+  return true;
+}
+
 void CSSDefaultStyleSheets::CollectFeaturesTo(const Document& document,
                                               RuleFeatureSet& features) {
   if (DefaultStyle())
@@ -380,6 +410,7 @@ void CSSDefaultStyleSheets::Trace(Visitor* visitor) const {
   visitor->Trace(mathml_style_sheet_);
   visitor->Trace(media_controls_style_sheet_);
   visitor->Trace(text_track_style_sheet_);
+  visitor->Trace(forced_colors_style_sheet_);
   visitor->Trace(fullscreen_style_sheet_);
   visitor->Trace(webxr_overlay_style_sheet_);
   visitor->Trace(marker_style_sheet_);

third_party/blink/renderer/core/css/css_default_style_sheets.h

@@ -51,6 +51,7 @@ class CSSDefaultStyleSheets final
   bool EnsureDefaultStyleSheetsForPseudoElement(PseudoId);
   bool EnsureDefaultStyleSheetForXrOverlay();
   void EnsureDefaultStyleSheetForFullscreen();
+  bool EnsureDefaultStyleSheetForForcedColors();
 
   RuleSet* DefaultStyle() { return default_style_.Get(); }
   RuleSet* DefaultMathMLStyle() { return default_mathml_style_.Get(); }
@@ -83,6 +84,9 @@ class CSSDefaultStyleSheets final
     return fullscreen_style_sheet_.Get();
   }
   StyleSheetContents* MarkerStyleSheet() { return marker_style_sheet_.Get(); }
+  StyleSheetContents* ForcedColorsStyleSheet() {
+    return forced_colors_style_sheet_.Get();
+  }
 
   CORE_EXPORT void PrepareForLeakDetection();
 
@@ -131,6 +135,7 @@ class CSSDefaultStyleSheets final
   Member<StyleSheetContents> fullscreen_style_sheet_;
   Member<StyleSheetContents> webxr_overlay_style_sheet_;
   Member<StyleSheetContents> marker_style_sheet_;
+  Member<StyleSheetContents> forced_colors_style_sheet_;
 
   std::unique_ptr<UAStyleSheetLoader> media_controls_style_sheet_loader_;
 };

third_party/blink/renderer/core/css/style_engine.cc

@@ -1377,6 +1377,17 @@ void StyleEngine::EnsureUAStyleForPseudoElement(PseudoId pseudo_id) {
   }
 }
 
+void StyleEngine::EnsureUAStyleForForcedColors() {
+  DCHECK(!IsHTMLImport());
+  DCHECK(global_rule_set_);
+  if (CSSDefaultStyleSheets::Instance()
+          .EnsureDefaultStyleSheetForForcedColors()) {
+    global_rule_set_->MarkDirty();
+    if (GetDocument().IsActive())
+      UpdateActiveStyle();
+  }
+}
+
 bool StyleEngine::HasRulesForId(const AtomicString& id) const {
   DCHECK(!IsHTMLImport());
   DCHECK(global_rule_set_);

third_party/blink/renderer/core/css/style_engine.h

@@ -294,6 +294,7 @@ class CORE_EXPORT StyleEngine final : public GarbageCollected<StyleEngine>,
   void EnsureUAStyleForXrOverlay();
   void EnsureUAStyleForElement(const Element&);
   void EnsureUAStyleForPseudoElement(PseudoId);
+  void EnsureUAStyleForForcedColors();
 
   void PlatformColorsChanged();
 

third_party/blink/renderer/core/dom/document.cc

@@ -878,13 +878,13 @@ Document::Document(const DocumentInit& initializer,
 
   lifecycle_.AdvanceTo(DocumentLifecycle::kInactive);
 
-  UpdateForcedColors();
-
   // Since CSSFontSelector requires Document::fetcher_ and StyleEngine owns
   // CSSFontSelector, need to initialize |style_engine_| after initializing
   // |fetcher_|.
   style_engine_ = MakeGarbageCollected<StyleEngine>(*this);
 
+  UpdateForcedColors();
+
   // The parent's parser should be suspended together with all the other
   // objects, else this new Document would have a new ExecutionContext which
   // suspended state would not match the one from the parent, and could start
@@ -8383,6 +8383,8 @@ void Document::UpdateForcedColors() {
                                    ? web_theme_engine->GetForcedColors()
                                    : ForcedColors::kNone;
   in_forced_colors_mode_ = forced_colors != ForcedColors::kNone;
+  if (in_forced_colors_mode_)
+    GetStyleEngine().EnsureUAStyleForForcedColors();
 }
 
 bool Document::InForcedColorsMode() const {