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

src/ic/ic.h

Index: src/ic/ic.h
diff --git a/src/ic/ic.h b/src/ic/ic.h
index e1facd6358313813f1a0bdfa9cb73510790b975e..e718dad7166a26f54fd55d37db546c99370f5d22 100644
--- a/src/ic/ic.h
+++ b/src/ic/ic.h
@@ -412,7 +412,6 @@ class KeyedLoadIC : public LoadIC {
     GenerateMiss(masm);
   }
   static void GenerateGeneric(MacroAssembler* masm);
-  static void GenerateString(MacroAssembler* masm);
 
   // Bit mask to be tested against bit field for the cases when
   // generic stub should go into slow case.
@@ -425,16 +424,14 @@ class KeyedLoadIC : public LoadIC {
   static Handle<Code> pre_monomorphic_stub(Isolate* isolate);
 
  protected:
-  Handle<Code> LoadElementStub(Handle<JSObject> receiver);
+  // receiver is HeapObject because it could be a String or a JSObject
+  Handle<Code> LoadElementStub(Handle<HeapObject> receiver);
   virtual Handle<Code> pre_monomorphic_stub() const {
     return pre_monomorphic_stub(isolate());
   }
 
  private:
   Handle<Code> generic_stub() const { return generic_stub(isolate()); }
-  Handle<Code> string_stub() {
-    return isolate()->builtins()->KeyedLoadIC_String();
-  }
 
   static void Clear(Isolate* isolate, Address address, Code* target,
                     ConstantPoolArray* constant_pool);