Check for cached transition to ExternalArray elements kind.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 68151dbf324c99699c880545606ec874734412f7..6d94c1006b1c582a0cfdd25e762383a7e6f40167 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3379,9 +3379,16 @@ static Map* FindClosestElementsTransition(Map* map, ElementsKind to_kind) {
       ? to_kind
       : TERMINAL_FAST_ELEMENTS_KIND;
 
-  // Support for legacy API.
+  // Support for legacy API: SetIndexedPropertiesTo{External,Pixel}Data
+  // allows to change elements from arbitrary kind to any

[Igor Sheludko, 2014/05/23 12:24:14]

nit: please reformat comment

+  // ExternalArray elements kind. Satisfy its requirements, checking whether
+  // we already have the cached transition.
   if (IsExternalArrayElementsKind(to_kind) &&
       !IsFixedTypedArrayElementsKind(map->elements_kind())) {
+    if (map->HasElementsTransition()) {
+        Map* next_map = map->elements_transition_map();
+        if (next_map->elements_kind() == to_kind) return next_map;
+    }
     return map;
   }