Oilpan: move mutation observers to the Oilpan heap.

Source/core/css/PropertySetCSSStyleDeclaration.cpp

Index: Source/core/css/PropertySetCSSStyleDeclaration.cpp
diff --git a/Source/core/css/PropertySetCSSStyleDeclaration.cpp b/Source/core/css/PropertySetCSSStyleDeclaration.cpp
index dbf13d03b62ee0cb13149edbe0ae0e09a3225714..9c1b6d878c14bf52aacb9a4387ea5827515e1019 100644
--- a/Source/core/css/PropertySetCSSStyleDeclaration.cpp
+++ b/Source/core/css/PropertySetCSSStyleDeclaration.cpp
@@ -41,6 +41,7 @@ namespace {
 
 class StyleAttributeMutationScope {
     WTF_MAKE_NONCOPYABLE(StyleAttributeMutationScope);
+    STACK_ALLOCATED();
 public:
     StyleAttributeMutationScope(AbstractPropertySetCSSStyleDeclaration* decl)
     {
@@ -114,8 +115,8 @@ private:
     static bool s_shouldNotifyInspector;
     static bool s_shouldDeliver;
 
-    OwnPtr<MutationObserverInterestGroup> m_mutationRecipients;
-    RefPtr<MutationRecord> m_mutation;
+    OwnPtrWillBeMember<MutationObserverInterestGroup> m_mutationRecipients;
+    RefPtrWillBeMember<MutationRecord> m_mutation;
 };
 
 unsigned StyleAttributeMutationScope::s_scopeCount = 0;