Add "has fast elements" bit to maps and use it in inlined keyed loads.

src/api.cc

 // Copyright 2009 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 2588 matching lines @@
                 "length exceeds max acceptable value")) {
     return;
   }
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
   if (!ApiCheck(!self->IsJSArray(),
                 "v8::Object::SetIndexedPropertiesToPixelData()",
                 "JSArray is not supported")) {
     return;
   }
   i::Handle<i::PixelArray> pixels = i::Factory::NewPixelArray(length, data);
+  self->set_map(
+      *i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map())));
   self->set_elements(*pixels);
 }
 
 
 bool v8::Object::HasIndexedPropertiesInPixelData() {
   ON_BAILOUT("v8::HasIndexedPropertiesInPixelData()", return false);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
   return self->HasPixelElements();
 }
 
@@ skipping 33 matching lines @@
     return;
   }
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
   if (!ApiCheck(!self->IsJSArray(),
                 "v8::Object::SetIndexedPropertiesToExternalArrayData()",
                 "JSArray is not supported")) {
     return;
   }
   i::Handle<i::ExternalArray> array =
       i::Factory::NewExternalArray(length, array_type, data);
+  self->set_map(
+      *i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map())));
   self->set_elements(*array);
 }
 
 
 bool v8::Object::HasIndexedPropertiesInExternalArrayData() {
   ON_BAILOUT("v8::HasIndexedPropertiesInExternalArrayData()", return false);
   i::Handle<i::JSObject> self = Utils::OpenHandle(this);
   return self->HasExternalArrayElements();
 }
 
@@ skipping 2041 matching lines @@
 
 
 char* HandleScopeImplementer::Iterate(ObjectVisitor* v, char* storage) {
   HandleScopeImplementer* thread_local =
       reinterpret_cast<HandleScopeImplementer*>(storage);
   thread_local->IterateThis(v);
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal