Refactor out assumption that one byte strings are ascii in utf8 processing.

src/handles.h

 // Copyright 2011 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 196 matching lines @@
 // an object of expected type, or the handle is an error if running out
 // of space or encountering an internal error.
 
 // Flattens a string.
 void FlattenString(Handle<String> str);
 
 // Flattens a string and returns the underlying external or sequential
 // string.
 Handle<String> FlattenGetString(Handle<String> str);
 
-int Utf8Length(Handle<String> str);
-
 Handle<Object> SetProperty(Isolate* isolate,
                            Handle<Object> object,
                            Handle<Object> key,
                            Handle<Object> value,
                            PropertyAttributes attributes,
                            StrictModeFlag strict_mode);
 
 Handle<Object> ForceSetProperty(Handle<JSObject> object,
                                 Handle<Object> key,
                                 Handle<Object> value,
@@ skipping 108 matching lines @@
   inline ~NoHandleAllocation();
  private:
   int level_;
   bool active_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_