Introduce ProcessYoungWeakReferences and process weak list of allocation sites just during full GCs.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 
 #include "src/allocation.h"
@@ skipping 1206 matching lines @@
 
     return false;
   }
 
   void UpdateNewSpaceReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
   void UpdateReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
-  void ProcessWeakReferences(WeakObjectRetainer* retainer);
+  void ProcessAllWeakReferences(WeakObjectRetainer* retainer);
+  void ProcessYoungWeakReferences(WeakObjectRetainer* retainer);
 
   void VisitExternalResources(v8::ExternalResourceVisitor* visitor);
 
   // An object should be promoted if the object has survived a
   // scavenge operation.
   inline bool ShouldBePromoted(Address old_address, int object_size);
 
   void ClearJSFunctionResultCaches();
 
   void ClearNormalizedMapCaches();
@@ skipping 1346 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_