Replace ICStub for array.length with hydrogen stub

src/hydrogen.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 903 matching lines @@
   HInstruction* BuildUncheckedMonomorphicElementAccess(
       HValue* object,
       HValue* key,
       HValue* val,
       HCheckMaps* mapcheck,
       bool is_js_array,
       ElementsKind elements_kind,
       bool is_store,
       Representation checked_index_representation = Representation::None());
 
+  HInstruction* BuildFastArrayLengthLoad(HValue* object);
+
   HInstruction* BuildStoreMap(HValue* object, HValue* map, BailoutId id);
   HInstruction* BuildStoreMap(HValue* object, Handle<Map> map, BailoutId id);
 
   class CheckBuilder {
    public:
     CheckBuilder(HGraphBuilder* builder, BailoutId id);
     ~CheckBuilder() {
       if (!finished_) End();
     }
 
@@ skipping 745 matching lines @@
   EmbeddedVector<char, 64> filename_;
   HeapStringAllocator string_allocator_;
   StringStream trace_;
   int indent_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_