Add a UseCounter for Object.observe

include/v8.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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 5128 matching lines @@
    * assigned numbers of existing items; add new features to the end of this
    * list.
    */
   enum UseCounterFeature {
     kUseAsm = 0,
     kBreakIterator = 1,
     kLegacyConst = 2,
     kMarkDequeOverflow = 3,
     kStoreBufferOverflow = 4,
     kSlotsBufferOverflow = 5,
+    kObjectObserve = 6,
     kUseCounterFeatureCount  // This enum value must be last.
   };
 
   typedef void (*UseCounterCallback)(Isolate* isolate,
                                      UseCounterFeature feature);
 
 
   /**
    * Creates a new isolate.  Does not change the currently entered
    * isolate.
@@ skipping 2899 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_