[proxies] Implement [[Delete]].

src/runtime/runtime-scopes.cc

 // Copyright 2014 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/frames-inl.h"
 #include "src/isolate-inl.h"
@@ skipping 885 matching lines @@
 
   // If the slot was found in a context, it should be DONT_DELETE.
   if (holder->IsContext()) {
     return isolate->heap()->false_value();
   }
 
   // The slot was found in a JSObject, either a context extension object,
   // the global object, or the subject of a with.  Try to delete it
   // (respecting DONT_DELETE).
   Handle<JSObject> object = Handle<JSObject>::cast(holder);
-  Handle<Object> result;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
-                                     JSReceiver::DeleteProperty(object, name));
-  return *result;
+  Maybe<bool> result = JSReceiver::DeleteProperty(object, name);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return isolate->heap()->ToBoolean(result.FromJust());
 }
 
 
 static Object* ComputeReceiverForNonGlobal(Isolate* isolate, JSObject* holder) {
   DCHECK(!holder->IsJSGlobalObject());
 
   // If the holder isn't a context extension object, we just return it
   // as the receiver. This allows arguments objects to be used as
   // receivers, but only if they are put in the context scope chain
   // explicitly via a with-statement.
@@ skipping 247 matching lines @@
 
   // Lookup in the initial Object.prototype object.
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Object::GetProperty(isolate->initial_object_prototype(), key));
   return *result;
 }
 }  // namespace internal
 }  // namespace v8