Implement UXTB and UXTH in the ARM integerated assembler.

src/DartARM32/assembler_arm.h

 // 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.
 //
 // This is forked from Dart revision df52deea9f25690eb8b66c5995da92b70f7ac1fe
 // Please update the (git) revision if we merge changes from Dart.
 // https://code.google.com/p/dart/wiki/GettingTheSource
 
 #ifndef VM_ASSEMBLER_ARM_H_
 #define VM_ASSEMBLER_ARM_H_
@@ skipping 1283 matching lines @@
                               intptr_t offset,
                               Register value_even,
                               Register value_odd,
                               Condition cond = AL);
   // Writes new_value to address and its shadow location, if enabled, after
   // verifying that its old value matches its shadow.
   void VerifiedWrite(const Address& address,
                      Register new_value,
                      FieldContent old_content);
 
+#if 0
+  // Added the following missing operations:
+  //
+  // ARM32::AssemblerARM::uxt() (uxtb and uxth).
+#endif
+
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM_H_