Implement for-in loop for proxies.

src/handles.h

Index: src/handles.h
diff --git a/src/handles.h b/src/handles.h
index d5521f89c1e6ef43e49ecc2880e9c26876bc5e31..25c69a413d57517bd289edca098fb9fcb45019a4 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -300,18 +300,19 @@ int GetScriptLineNumberSafe(Handle<Script> script, int code_position);
 
 // Computes the enumerable keys from interceptors. Used for debug mirrors and
 // by GetKeysInFixedArrayFor below.
-v8::Handle<v8::Array> GetKeysForNamedInterceptor(Handle<JSObject> receiver,
+v8::Handle<v8::Array> GetKeysForNamedInterceptor(Handle<JSReceiver> receiver,
                                                  Handle<JSObject> object);
-v8::Handle<v8::Array> GetKeysForIndexedInterceptor(Handle<JSObject> receiver,
+v8::Handle<v8::Array> GetKeysForIndexedInterceptor(Handle<JSReceiver> receiver,
                                                    Handle<JSObject> object);
 
 enum KeyCollectionType { LOCAL_ONLY, INCLUDE_PROTOS };
 
 // Computes the enumerable keys for a JSObject. Used for implementing
 // "for (n in object) { }".
-Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSObject> object,
-                                          KeyCollectionType type);
-Handle<JSArray> GetKeysFor(Handle<JSObject> object);
+Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSReceiver> object,
+                                          KeyCollectionType type,
+                                          bool* threw);
+Handle<JSArray> GetKeysFor(Handle<JSReceiver> object, bool* threw);
 Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object,
                                        bool cache_result);