Bug 1449103 part 2 - Make CSSKeyframesRule inherit from Rule directly. r=emilio

The spec doesn't say CSSKeyframesRule needs to inherit CSSGroupingRule.
It inherited GroupRule because Gecko's keyframes rule implementation
relies on that to manage its children.

MozReview-Commit-ID: CnVP2tozwQU

--HG--
extra : rebase_source : 63c61d7b7d003ff82bd73e183516f6076a2dafb6

layout/style/CSSKeyframesRule.h

@@ -7,20 +7,22 @@
 #ifndef mozilla_dom_CSSKeyframesRule_h
 #define mozilla_dom_CSSKeyframesRule_h
 
-#include "mozilla/css/GroupRule.h"
+#include "mozilla/css/Rule.h"
 #include "mozilla/dom/CSSKeyframeRule.h"
 
 namespace mozilla {
 namespace dom {
 
-class CSSKeyframesRule : public css::GroupRule
+class CSSKeyframesRule : public css::Rule
 {
 protected:
-  using css::GroupRule::GroupRule;
+  using css::Rule::Rule;
   virtual ~CSSKeyframesRule() {}
 
 public:
   int32_t GetType() const final { return Rule::KEYFRAMES_RULE; }
+  // Let's not worry for now about sorting out whether we're a leaf or not.
+  bool IsCCLeaf() const override { return false; }
 
   // WebIDL interface
   uint16_t Type() const final { return CSSRuleBinding::KEYFRAMES_RULE; }

layout/style/ServoKeyframesRule.cpp

@@ -158,10 +158,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 ServoKeyframesRule::ServoKeyframesRule(RefPtr<RawServoKeyframesRule> aRawRule,
                                        uint32_t aLine, uint32_t aColumn)
-  // Although this class inherits from GroupRule, we don't want to use
-  // it at all, so it is fine to call the constructor for Gecko. We can
-  // make CSSKeyframesRule inherit from Rule directly once we can get
-  // rid of nsCSSKeyframeRule.
   : dom::CSSKeyframesRule(aLine, aColumn)
   , mRawRule(Move(aRawRule))
 {
@@ -347,7 +343,6 @@ ServoKeyframesRule::FindRule(const nsAString& aKey)
 ServoKeyframesRule::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
 {
   size_t n = aMallocSizeOf(this);
-  n += GroupRule::SizeOfExcludingThis(aMallocSizeOf);
   if (mKeyframeList) {
     n += mKeyframeList->SizeOfIncludingThis(aMallocSizeOf);
   }