[gin] Allow interceptors to signal whether a they intercepted something

gin/interceptor.h

 // Copyright 2014 The Chromium 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 GIN_INTERCEPTOR_H_
 #define GIN_INTERCEPTOR_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "gin/gin_export.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 
 class WrappableBase;
 
 // Base class for gin::Wrappable-derived classes that want to implement a
 // property interceptor.
 class GIN_EXPORT NamedPropertyInterceptor {
  public:
   NamedPropertyInterceptor(v8::Isolate* isolate, WrappableBase* base);
   virtual ~NamedPropertyInterceptor();
 
   virtual v8::Local<v8::Value> GetNamedProperty(v8::Isolate* isolate,
                                                 const std::string& property);
-  virtual void SetNamedProperty(v8::Isolate* isolate,
+  // Return true if the set was interecepted.
+  virtual bool SetNamedProperty(v8::Isolate* isolate,
                                 const std::string& property,
                                 v8::Local<v8::Value> value);
   virtual std::vector<std::string> EnumerateNamedProperties(
       v8::Isolate* isolate);
 
  private:
   v8::Isolate* isolate_;
   WrappableBase* base_;
 
   DISALLOW_COPY_AND_ASSIGN(NamedPropertyInterceptor);
 };
 
 class GIN_EXPORT IndexedPropertyInterceptor {
  public:
   IndexedPropertyInterceptor(v8::Isolate* isolate, WrappableBase* base);
   virtual ~IndexedPropertyInterceptor();
 
   virtual v8::Local<v8::Value> GetIndexedProperty(v8::Isolate* isolate,
                                                   uint32_t index);
-  virtual void SetIndexedProperty(v8::Isolate* isolate,
+  // Return true if the set was interecepted.
+  virtual bool SetIndexedProperty(v8::Isolate* isolate,
                                   uint32_t index,
                                   v8::Local<v8::Value> value);
   virtual std::vector<uint32_t> EnumerateIndexedProperties(
       v8::Isolate* isolate);
 
  private:
   v8::Isolate* isolate_;
   WrappableBase* base_;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedPropertyInterceptor);
 };
 
 }  // namespace gin
 
 #endif  // GIN_INTERCEPTOR_H_