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

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2290 matching lines @@
 
   // Extend the receiver with a single fast property appeared first in the
   // passed map. This also extends the property backing store if necessary.
   static void AllocateStorageForMap(Handle<JSObject> object, Handle<Map> map);
 
   // Migrates the given object to a map whose field representations are the
   // lowest upper bound of all known representations for that field.
   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.
   Object* GetNormalizedProperty(const LookupResult* result);
   static Handle<Object> GetNormalizedProperty(Handle<JSObject> object,
                                               const LookupResult* result);
 
   // Sets the property value in a normalized object given a lookup result.
   // Handles the special representation of JS global objects.
   static void SetNormalizedProperty(Handle<JSObject> object,
@@ skipping 4128 matching lines @@
   inline void set_migration_target(bool value);
   inline bool is_migration_target();
   inline void deprecate();
   inline bool is_deprecated();
   inline bool CanBeDeprecated();
   // Returns a non-deprecated version of the input. If the input was not
   // deprecated, it is directly returned. Otherwise, the non-deprecated version
   // 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,
                                           Descriptor* descriptor,
                                           TransitionFlag flag);
   static Handle<Map> CopyReplaceDescriptor(Handle<Map> map,
                                            Handle<DescriptorArray> descriptors,
                                            Descriptor* descriptor,
                                            int index,
                                            TransitionFlag flag);
@@ skipping 4809 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_