Refactor the Heap into ThreadHeap to prepare for per thread heaps

third_party/WebKit/Source/platform/WebThreadSupportingGC.h

Index: third_party/WebKit/Source/platform/WebThreadSupportingGC.h
diff --git a/third_party/WebKit/Source/platform/WebThreadSupportingGC.h b/third_party/WebKit/Source/platform/WebThreadSupportingGC.h
index 405401eb58d6dac33394a302c6ffcbcc82573ce2..2fce5c63598b86e719038a0384ce7b86b77877f1 100644
--- a/third_party/WebKit/Source/platform/WebThreadSupportingGC.h
+++ b/third_party/WebKit/Source/platform/WebThreadSupportingGC.h
@@ -27,8 +27,8 @@ namespace blink {
 class PLATFORM_EXPORT WebThreadSupportingGC final {
     WTF_MAKE_NONCOPYABLE(WebThreadSupportingGC);
 public:
-    static PassOwnPtr<WebThreadSupportingGC> create(const char* name);
-    static PassOwnPtr<WebThreadSupportingGC> createForThread(WebThread*);
+    static PassOwnPtr<WebThreadSupportingGC> create(const char* name, bool isolated=false);
+    static PassOwnPtr<WebThreadSupportingGC> createForThread(WebThread*, bool isolated=false);
     ~WebThreadSupportingGC();
 
     void postTask(const WebTraceLocation& location, WebTaskRunner::Task* task)
@@ -66,7 +66,7 @@ public:
     }
 
 private:
-    WebThreadSupportingGC(const char* name, WebThread*);
+    WebThreadSupportingGC(const char* name, WebThread*, bool isolated=false);
 
     OwnPtr<GCTaskRunner> m_gcTaskRunner;
 
@@ -75,6 +75,7 @@ private:
     // existing thread via createForThread().
     WebThread* m_thread = nullptr;
     OwnPtr<WebThread> m_owningThread;
+    bool m_isolated;
 };
 
 }