Refactor the Heap into ThreadHeap to prepare for per thread heaps

third_party/WebKit/Source/platform/heap/Visitor.h

Index: third_party/WebKit/Source/platform/heap/Visitor.h
diff --git a/third_party/WebKit/Source/platform/heap/Visitor.h b/third_party/WebKit/Source/platform/heap/Visitor.h
index 443db172a7ead4857fe943db6881ba5ca5b2d90c..3943142a2dea80c7499d836917c49b66d425f76c 100644
--- a/third_party/WebKit/Source/platform/heap/Visitor.h
+++ b/third_party/WebKit/Source/platform/heap/Visitor.h
@@ -53,6 +53,7 @@ template<typename T> class TraceTrait;
 template<typename T> class TraceEagerlyTrait;
 class ThreadState;
 class Visitor;
+class VisitorScope;
 
 // The TraceMethodDelegate is used to convert a trace method for type T to a TraceCallback.
 // This allows us to pass a type's trace method as a parameter to the PersistentNode
@@ -123,6 +124,8 @@ public:
 template<typename Derived>
 class VisitorHelper {
 public:
+    VisitorHelper(VisitorScope* visitorScope) : m_visitorScope(visitorScope) {}
+
     // One-argument templated mark method. This uses the static type of
     // the argument to get the TraceTrait. By default, the mark method
     // of the TraceTrait just calls the virtual two-argument mark method on this
@@ -283,9 +286,13 @@ public:
         Derived::fromHelper(this)->registerWeakMembers(object, object, callback);
     }
 
+    inline VisitorScope* visitorScope() const { return m_visitorScope; }
+
 private:
     template<typename T>
     static void handleWeakCell(Visitor* self, void* object);
+
+    VisitorScope* m_visitorScope;
 };
 
 // Visitor is used to traverse the Blink object graph. Used for the
@@ -374,8 +381,9 @@ public:
     inline MarkingMode markingMode() const { return m_markingMode; }
 
 protected:
-    explicit Visitor(MarkingMode markingMode)
-        : m_markingMode(markingMode)
+    explicit Visitor(MarkingMode markingMode, VisitorScope* visitorScope)
+        : VisitorHelper(visitorScope)
+        , m_markingMode(markingMode)
     { }
 
     virtual void registerWeakCellWithCallback(void**, WeakCallback) = 0;
@@ -387,12 +395,13 @@ private:
     bool m_isGlobalMarkingVisitor;
 };
 
-class VisitorScope final {
+class PLATFORM_EXPORT VisitorScope final {

[haraken, 2016/02/29 11:17:45]

Can we unify the VisitorScope and the Visitor into one class (before landing
this CL)? Then you don't need to look up the VisitorScope from the Visitor.
Conceptually, the VisitorScope and the Visitor should be the same thing.

class Visitor {
  STACK_ALLOCATED();
  ...;
  ThreadState* m_state;
};

[keishi, 2016/03/02 06:01:03]

Created https://codereview.chromium.org/1753623002/

     STACK_ALLOCATED();
 public:
     VisitorScope(ThreadState*, BlinkGC::GCType);
     ~VisitorScope();
     Visitor* visitor() const { return m_visitor.get(); }
+    Heap& heap() const { return m_state->heap(); }
 
 private:
     ThreadState* m_state;