Preallocate transitioned maps for TypedArrays.

src/api.cc

 // 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 5935 matching lines @@
   obj->set_byte_length(*byte_length_object);
 
   i::Handle<i::Object> length_object = isolate->factory()->NewNumber(
         static_cast<double>(length));
   obj->set_length(*length_object);
 
   i::Handle<i::ExternalArray> elements =
       isolate->factory()->NewExternalArray(
           static_cast<int>(length), array_type,
           static_cast<uint8_t*>(buffer->backing_store()) + byte_offset);
-  i::Handle<i::Map> map =
-      isolate->factory()->GetElementsTransitionMap(
-          obj, elements_kind);
-  obj->set_map(*map);
   obj->set_elements(*elements);
   return obj;
 }
 
 
 #define TYPED_ARRAY_NEW(TypedArray, element_type, array_type, elements_kind) \
   Local<TypedArray> TypedArray::New(Handle<ArrayBuffer> array_buffer,        \
                                     size_t byte_offset, size_t length) {     \
     i::Isolate* isolate = i::Isolate::Current();                             \
     EnsureInitializedForIsolate(isolate,                                     \
@@ skipping 1717 matching lines @@
 
   v->VisitPointers(blocks_.first(), first_block_limit_);
 
   for (int i = 1; i < blocks_.length(); i++) {
     v->VisitPointers(blocks_[i], &blocks_[i][kHandleBlockSize]);
   }
 }
 
 
 } }  // namespace v8::internal