Add optimized loads from ExternalUint8ClampedArrays.

runtime/vm/flow_graph_compiler_x64.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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "lib/error.h"
@@ skipping 1544 matching lines @@
 }
 
 
 Address FlowGraphCompiler::ExternalElementAddressForRegIndex(
     intptr_t cid,
     intptr_t index_scale,
     Register array,
     Register index) {
   switch (cid) {
     case kExternalUint8ArrayCid:
+    case kExternalUint8ClampedArrayCid:
       return Address(array, index, ToScaleFactor(index_scale), 0);
     default:
       UNIMPLEMENTED();
       return Address(SPREG, 0);
   }
 }
 
 
 #undef __
 #define __ compiler_->assembler()->
@@ skipping 124 matching lines @@
 void ParallelMoveResolver::Exchange(const Address& mem1, const Address& mem2) {
   __ Exchange(mem1, mem2);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64