Fix CurrentMapForDeprecated() to return MaybeHandle instead of a null handle.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d926165c3e06e358ff595567f5ba58a175286743..b4015eef4ecbc9fd9ba8a15afd67da65b159cd06 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2308,8 +2308,8 @@ class JSObject: public JSReceiver {
   static void MigrateInstance(Handle<JSObject> instance);
 
   // Migrates the given object only if the target map is already available,
-  // or returns an empty handle if such a map is not yet available.
-  static Handle<Object> TryMigrateInstance(Handle<JSObject> instance);
+  // or returns false if such a map is not yet available.
+  static bool TryMigrateInstance(Handle<JSObject> instance);
 
   // Retrieve a value in a normalized object given a lookup result.
   // Handles the special representation of JS global objects.
@@ -6458,9 +6458,9 @@ class Map: public HeapObject {
   // is found by re-transitioning from the root of the transition tree using the
   // descriptor array of the map. Returns NULL if no updated map is found.
   // This method also applies any pending migrations along the prototype chain.
-  static Handle<Map> CurrentMapForDeprecated(Handle<Map> map);
+  static MaybeHandle<Map> CurrentMapForDeprecated(Handle<Map> map);

[Yang, 2014/04/25 11:48:06]

We generally mark functions that return MaybeHandle with MUST_USE_RESULT to
enforce result checking. Maybe we want to do it here as well?

[Benedikt Meurer, 2014/04/26 10:12:42]

Done.

   // Same as above, but does not touch the prototype chain.
-  static Handle<Map> CurrentMapForDeprecatedInternal(Handle<Map> map);
+  static MaybeHandle<Map> CurrentMapForDeprecatedInternal(Handle<Map> map);
 
   static Handle<Map> CopyDropDescriptors(Handle<Map> map);
   static Handle<Map> CopyInsertDescriptor(Handle<Map> map,