Intrinsify OnebyteString's substringUnchecked. Significant performance improvement on Json benchmar…

runtime/vm/intrinsifier_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intrinsifier.h"
 #include "vm/object.h"
 
@@ skipping 317 matching lines @@
 
 bool Intrinsifier::String_getIsEmpty(Assembler* assembler) {
   return false;
 }
 
 
 bool Intrinsifier::OneByteString_getHashCode(Assembler* assembler) {
   return false;
 }
 
+
+bool Intrinsifier::OneByteString_substringUnchecked(Assembler* assembler) {
+  return false;
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM