Removed a bunch of GetExistingThreadLocal calls by threading the Isolate.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 771 matching lines @@
   }
 
   template<typename T>
   inline bool To(T** obj) {
     if (IsFailure()) return false;
     *obj = T::cast(reinterpret_cast<Object*>(this));
     return true;
   }
 
   template<typename T>
-  inline bool ToHandle(Handle<T>* obj) {
+    inline bool ToHandle(Handle<T>* obj, Isolate* isolate) {
     if (IsFailure()) return false;
-    *obj = handle(T::cast(reinterpret_cast<Object*>(this)));
+    *obj = handle(T::cast(reinterpret_cast<Object*>(this)), isolate);
     return true;
   }
 
 #ifdef OBJECT_PRINT
   // Prints this object with details.
   inline void Print() {
     Print(stdout);
   }
   inline void PrintLn() {
     PrintLn(stdout);
@@ skipping 8213 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_