Make custom element default style accept array of stylesheets

After developer feedback on ergonomics, having a way to add multiple
stylesheets as the default style for a custom element seems to be
preferred. This CL changes custom element default style to handle
multiple stylesheets.

Bug: 824684
Change-Id: Ie0a130db42425396132ed48237e4b24c34243031
Reviewed-on: https://chromium-review.googlesource.com/c/1257468Reviewed-by: Hayato Ito <hayato@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597425}

third_party/blink/renderer/bindings/core/v8/script_custom_element_definition.cc

@@ -191,7 +191,7 @@ HTMLElement* ScriptCustomElementDefinition::CreateAutonomousCustomElementSync(
   if (element->prefix() != tag_name.Prefix())
     element->SetTagNameForCreateElementNS(tag_name);
   DCHECK_EQ(element->GetCustomElementState(), CustomElementState::kCustom);
-  AddDefaultStyle(element);
+  AddDefaultStylesTo(*element);
   return ToHTMLElement(element);
 }
 

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

@@ -213,10 +213,11 @@ static void MatchCustomElementRules(const Element& element,
     return;
   if (CustomElementDefinition* definition =
           element.GetCustomElementDefinition()) {
-    if (CSSStyleSheet* default_style = definition->DefaultStyleSheet()) {
-      collector.CollectMatchingRules(
-          MatchRequest(element.GetDocument().GetStyleEngine().RuleSetForSheet(
-              *default_style)));
+    if (definition->HasDefaultStyleSheets()) {
+      for (CSSStyleSheet* style : definition->DefaultStyleSheets()) {
+        collector.CollectMatchingRules(MatchRequest(
+            element.GetDocument().GetStyleEngine().RuleSetForSheet(*style)));
+      }
     }
   }
 }

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

@@ -318,11 +318,13 @@ void StyleEngine::AdoptedStyleSheetsWillChange(TreeScope& tree_scope,
   SetNeedsActiveStyleUpdate(tree_scope);
 }
 
-void StyleEngine::AddedCustomElementDefaultStyle(CSSStyleSheet* default_style) {
+void StyleEngine::AddedCustomElementDefaultStyles(
+    const HeapVector<Member<CSSStyleSheet>>& default_styles) {
   if (!RuntimeEnabledFeatures::CustomElementDefaultStyleEnabled() ||
       GetDocument().IsDetached())
     return;
-  custom_element_default_style_sheets_.insert(default_style);
+  for (CSSStyleSheet* sheet : default_styles)
+    custom_element_default_style_sheets_.insert(sheet);
   global_rule_set_->MarkDirty();
 }
 

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

@@ -133,7 +133,8 @@ class CORE_EXPORT StyleEngine final
   void AdoptedStyleSheetsWillChange(TreeScope&,
                                     StyleSheetList* old_sheets,
                                     StyleSheetList* new_sheets);
-  void AddedCustomElementDefaultStyle(CSSStyleSheet* default_style);
+  void AddedCustomElementDefaultStyles(
+      const HeapVector<Member<CSSStyleSheet>>& default_styles);
   void MediaQueriesChangedInScope(TreeScope&);
   void WatchedSelectorsChanged();
   void InitialStyleChanged();

third_party/blink/renderer/core/dom/element_definition_options.idl

@@ -4,5 +4,5 @@
 // Spec: https://html.spec.whatwg.org/#elementdefinitionoptions
 dictionary ElementDefinitionOptions {
     DOMString? extends = null;
-    CSSStyleSheet style;
+    sequence<CSSStyleSheet> styles;
 };

third_party/blink/renderer/core/html/custom/custom_element_definition.cc

@@ -4,7 +4,6 @@
 
 #include "third_party/blink/renderer/core/html/custom/custom_element_definition.h"
 #include "third_party/blink/renderer/core/css/css_import_rule.h"
-#include "third_party/blink/renderer/core/css/css_style_sheet.h"
 #include "third_party/blink/renderer/core/css/style_change_reason.h"
 #include "third_party/blink/renderer/core/css/style_engine.h"
 #include "third_party/blink/renderer/core/css/style_sheet_contents.h"
@@ -39,7 +38,7 @@ CustomElementDefinition::~CustomElementDefinition() = default;
 
 void CustomElementDefinition::Trace(blink::Visitor* visitor) {
   visitor->Trace(construction_stack_);
-  visitor->Trace(default_style_sheet_);
+  visitor->Trace(default_style_sheets_);
 }
 
 static String ErrorMessageForConstructorResult(Element* element,
@@ -207,30 +206,32 @@ void CustomElementDefinition::Upgrade(Element* element) {
   }
 
   element->SetCustomElementDefinition(this);
-  AddDefaultStyle(element);
+  AddDefaultStylesTo(*element);
 }
 
-void CustomElementDefinition::AddDefaultStyle(Element* element) {
-  if (!RuntimeEnabledFeatures::CustomElementDefaultStyleEnabled())
+void CustomElementDefinition::AddDefaultStylesTo(Element& element) {
+  if (!RuntimeEnabledFeatures::CustomElementDefaultStyleEnabled() ||
+      !HasDefaultStyleSheets())
     return;
-  CSSStyleSheet* default_style = DefaultStyleSheet();
-  if (!default_style)
-    return;
-  Document* associated_document = default_style->AssociatedDocument();
-  if (associated_document && associated_document != &element->GetDocument()) {
-    // Throw exception here?
+  const auto& default_styles = DefaultStyleSheets();
+  for (CSSStyleSheet* style : default_styles) {
+    Document* associated_document = style->AssociatedDocument();
+    if (associated_document && associated_document != &element.GetDocument()) {
+      // No spec yet, but for now we forbid usage of other document's
+      // constructed stylesheet.
       return;
     }
+  }
   if (!added_default_style_sheet_) {
-    element->GetDocument().GetStyleEngine().AddedCustomElementDefaultStyle(
-        default_style);
+    element.GetDocument().GetStyleEngine().AddedCustomElementDefaultStyles(
+        default_styles);
     added_default_style_sheet_ = true;
-    const AtomicString& local_tag_name =
-        element->LocalNameForSelectorMatching();
-    default_style->AddToCustomElementTagNames(local_tag_name);
+    const AtomicString& local_tag_name = element.LocalNameForSelectorMatching();
+    for (CSSStyleSheet* sheet : default_styles)
+      sheet->AddToCustomElementTagNames(local_tag_name);
   }
-  element->SetNeedsStyleRecalc(
-      kLocalStyleChange, StyleChangeReasonForTracing::Create(
+  element.SetNeedsStyleRecalc(kLocalStyleChange,
+                              StyleChangeReasonForTracing::Create(
                                   StyleChangeReason::kActiveStylesheetsUpdate));
 }
 

third_party/blink/renderer/core/html/custom/custom_element_definition.h

@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_value.h"
 #include "third_party/blink/renderer/core/core_export.h"
+#include "third_party/blink/renderer/core/css/css_style_sheet.h"
 #include "third_party/blink/renderer/core/dom/create_element_flags.h"
 #include "third_party/blink/renderer/core/html/custom/custom_element_descriptor.h"
 #include "third_party/blink/renderer/platform/bindings/name_client.h"
@@ -18,7 +19,6 @@
 
 namespace blink {
 
-class CSSStyleSheet;
 class Document;
 class Element;
 class ExceptionState;
@@ -91,11 +91,18 @@ class CORE_EXPORT CustomElementDefinition
                                        const AtomicString& old_value,
                                        const AtomicString& new_value);
 
-  void SetDefaultStyleSheet(CSSStyleSheet& default_style_sheet) {
-    default_style_sheet_ = default_style_sheet;
+  void SetDefaultStyleSheets(
+      const HeapVector<Member<CSSStyleSheet>>& default_style_sheets) {
+    default_style_sheets_ = default_style_sheets;
   }
 
-  CSSStyleSheet* DefaultStyleSheet() const { return default_style_sheet_; }
+  const HeapVector<Member<CSSStyleSheet>>& DefaultStyleSheets() const {
+    return default_style_sheets_;
+  }
+
+  bool HasDefaultStyleSheets() const {
+    return !default_style_sheets_.IsEmpty();
+  }
 
   class CORE_EXPORT ConstructionStackScope final {
     STACK_ALLOCATED();
@@ -117,7 +124,7 @@ class CORE_EXPORT CustomElementDefinition
   CustomElementDefinition(const CustomElementDescriptor&,
                           const HashSet<AtomicString>& observed_attributes);
 
-  void AddDefaultStyle(Element*);
+  void AddDefaultStylesTo(Element&);
 
   virtual bool RunConstructor(Element*) = 0;
 
@@ -133,7 +140,7 @@ class CORE_EXPORT CustomElementDefinition
   bool has_style_attribute_changed_callback_;
   bool added_default_style_sheet_ = false;
 
-  Member<CSSStyleSheet> default_style_sheet_;
+  HeapVector<Member<CSSStyleSheet>> default_style_sheets_;
 
   void EnqueueAttributeChangedCallbackForAllAttributes(Element*);
 

third_party/blink/renderer/core/html/custom/custom_element_registry.cc

@@ -212,8 +212,9 @@ CustomElementDefinition* CustomElementRegistry::DefineInternal(
   CHECK(!exception_state.HadException());
   CHECK(definition->Descriptor() == descriptor);
   if (RuntimeEnabledFeatures::CustomElementDefaultStyleEnabled() &&
-      options.hasStyle())
-    definition->SetDefaultStyleSheet(*options.style());
+      options.hasStyles())
+    definition->SetDefaultStyleSheets(options.styles());
+
   definitions_.emplace_back(definition);
   NameIdMap::AddResult result = name_id_map_.insert(descriptor.GetName(), id);
   CHECK(result.is_new_entry);