Support fast case for-in in Crankshaft.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 8b994eaed56872d74ada04d7870610c4a49e795a..4696d4e343d15f7bdf432c4089fa1bd7e3ab6e0d 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2412,7 +2412,9 @@ class DescriptorArray: public FixedArray {
 
   // Initialize or change the enum cache,
   // using the supplied storage for the small "bridge".
-  void SetEnumCache(FixedArray* bridge_storage, FixedArray* new_cache);
+  void SetEnumCache(FixedArray* bridge_storage,
+                    FixedArray* new_cache,
+                    Object* new_index_cache);
 
   // Accessors for fetching instance descriptor at descriptor number.
   inline String* GetKey(int descriptor_number);
@@ -2516,9 +2518,10 @@ class DescriptorArray: public FixedArray {
   static const int kFirstIndex = 3;
 
   // The length of the "bridge" to the enum cache.
-  static const int kEnumCacheBridgeLength = 2;
+  static const int kEnumCacheBridgeLength = 3;
   static const int kEnumCacheBridgeEnumIndex = 0;
   static const int kEnumCacheBridgeCacheIndex = 1;
+  static const int kEnumCacheBridgeIndicesCacheIndex = 2;
 
   // Layout description.
   static const int kBitField3StorageOffset = FixedArray::kHeaderSize;