Fix LoadOptimizer's handling of load/stores with constant indices for TypedData.

runtime/vm/bitfield.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_BITFIELD_H_
 #define VM_BITFIELD_H_
 
 namespace dart {
 
 static const uword kUwordOne = 1U;
 
 // BitField is a template for encoding and decoding a bit field inside
 // an unsigned machine word.
 template<typename T, int position, int size>
 class BitField {
  public:
+  static const intptr_t kNextBit = position + size;
+
   // Tells whether the provided value fits into the bit field.
   static bool is_valid(T value) {
     return (static_cast<uword>(value) & ~((kUwordOne << size) - 1)) == 0;
   }
 
   // Returns a uword mask of the bit field.
   static uword mask() {
     return (kUwordOne << size) - 1;
   }
 
@@ skipping 31 matching lines @@
   static uword update(T value, uword original) {
     ASSERT(is_valid(value));
     return (static_cast<uword>(value) << position) |
         (~mask_in_place() & original);
   }
 };
 
 }  // namespace dart
 
 #endif  // VM_BITFIELD_H_