Improve speed of Utf8Write by always flattening the string first and

src/objects.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 6039 matching lines @@
   SmartArrayPointer<char> ToCString(AllowNullsFlag allow_nulls,
                                     RobustnessFlag robustness_flag,
                                     int offset,
                                     int length,
                                     int* length_output = 0);
   SmartArrayPointer<char> ToCString(
       AllowNullsFlag allow_nulls = DISALLOW_NULLS,
       RobustnessFlag robustness_flag = FAST_STRING_TRAVERSAL,
       int* length_output = 0);
 
-  int Utf8Length();
+  inline int Utf8Length() { return Utf8Length(this, 0, length()); }
+  static int Utf8Length(String* input, int from, int to);
 
   // Return a 16 bit Unicode representation of the string.
   // The string should be nearly flat, otherwise the performance of
   // of this method may be very bad.  Setting robustness_flag to
   // ROBUST_STRING_TRAVERSAL invokes behaviour that is robust  This means it
   // handles unexpected data without causing assert failures and it does not
   // do any heap allocations.  This is useful when printing stack traces.
   SmartArrayPointer<uc16> ToWideCString(
       RobustnessFlag robustness_flag = FAST_STRING_TRAVERSAL);
 
@@ skipping 1518 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_