Eliminate special keyed load string stub in favor of uniform handlers.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 6106 matching lines @@
 
   bool CanTransition() {
     // Only JSObject and subtypes have map transitions and back pointers.
     STATIC_ASSERT(LAST_TYPE == LAST_JS_OBJECT_TYPE);
     return instance_type() >= FIRST_JS_OBJECT_TYPE;
   }
 
   bool IsJSObjectMap() {
     return instance_type() >= FIRST_JS_OBJECT_TYPE;
   }
+  bool IsStringMap() { return instance_type() < FIRST_NONSTRING_TYPE; }
   bool IsJSProxyMap() {
     InstanceType type = instance_type();
     return FIRST_JS_PROXY_TYPE <= type && type <= LAST_JS_PROXY_TYPE;
   }
   bool IsJSGlobalProxyMap() {
     return instance_type() == JS_GLOBAL_PROXY_TYPE;
   }
   bool IsJSGlobalObjectMap() {
     return instance_type() == JS_GLOBAL_OBJECT_TYPE;
   }
@@ skipping 4668 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_