CSS: Handle ::part rules when building RuleSets.

Add a part_pseudo_rules vector to RuleSet to hold rules with ::part
selectors and update RuleSet::FindBestRuleSetAndAdd to populate this.


Bug: 805271
Change-Id: If18cabbd8c933f49a252e2f659246cb0e0471e3f
Reviewed-on: https://chromium-review.googlesource.com/972766
Commit-Queue: Fergal Daly <fergal@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544969}

third_party/WebKit/Source/core/css/RuleSet.cpp

@@ -208,6 +208,11 @@ bool RuleSet::FindBestRuleSetAndAdd(const CSSSelector& component,
     case CSSSelector::kPseudoHostContext:
       shadow_host_rules_.push_back(rule_data);
       return true;
+    case CSSSelector::kPseudoPart:
+      if (RuntimeEnabledFeatures::CSSPartPseudoElementEnabled()) {
+        part_pseudo_rules_.push_back(rule_data);
+      }
+      return true;
     default:
       break;
   }
@@ -369,6 +374,7 @@ void RuleSet::CompactRules() {
   font_face_rules_.ShrinkToFit();
   keyframes_rules_.ShrinkToFit();
   deep_combinator_or_shadow_pseudo_rules_.ShrinkToFit();
+  part_pseudo_rules_.ShrinkToFit();
   content_pseudo_element_rules_.ShrinkToFit();
   slotted_pseudo_element_rules_.ShrinkToFit();
 }
@@ -402,6 +408,7 @@ void RuleSet::Trace(blink::Visitor* visitor) {
   visitor->Trace(font_face_rules_);
   visitor->Trace(keyframes_rules_);
   visitor->Trace(deep_combinator_or_shadow_pseudo_rules_);
+  visitor->Trace(part_pseudo_rules_);
   visitor->Trace(content_pseudo_element_rules_);
   visitor->Trace(slotted_pseudo_element_rules_);
   visitor->Trace(pending_rules_);

third_party/WebKit/Source/core/css/RuleSet.h

@@ -218,6 +218,10 @@ class CORE_EXPORT RuleSet : public GarbageCollectedFinalized<RuleSet> {
     DCHECK(!pending_rules_);
     return &shadow_host_rules_;
   }
+  const HeapVector<RuleData>* PartPseudoRules() const {
+    DCHECK(!pending_rules_);
+    return &part_pseudo_rules_;
+  }
   const HeapVector<Member<StyleRulePage>>& PageRules() const {
     DCHECK(!pending_rules_);
     return page_rules_;
@@ -318,6 +322,7 @@ class CORE_EXPORT RuleSet : public GarbageCollectedFinalized<RuleSet> {
   HeapVector<RuleData> focus_pseudo_class_rules_;
   HeapVector<RuleData> universal_rules_;
   HeapVector<RuleData> shadow_host_rules_;
+  HeapVector<RuleData> part_pseudo_rules_;
   RuleFeatureSet features_;
   HeapVector<Member<StyleRulePage>> page_rules_;
   HeapVector<Member<StyleRuleFontFace>> font_face_rules_;