Fix build failures on Win64 since r14215.

src/global-handles.cc

 // Copyright 2009 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 570 matching lines @@
 
   // During the iteration, some of the elements of object_groups are
   // deleted. This is done by moving surviving elements at the front of the list
   // and deleting from the end. This index tracks where the next surviving
   // element should be moved.
   int surviving_element_index = 0;
   int info_index = 0;  // For iterating retainer_infos_.
   int surviving_info_index = 0;
 
   UniqueId current_group_id(0);
-  size_t current_group_start = 0;
+  int current_group_start = 0;
   bool any_group_was_visited = false;
 
   for (int i = 0; i <= object_groups_.length(); ++i) {
     if (i == 0)
       current_group_id = object_groups_[i].id;
     if (i == object_groups_.length() ||
         current_group_id != object_groups_[i].id) {
       // Group detected: objects in indices [current_group_start, i[.
       bool group_should_be_visited = false;
       for (int j = current_group_start; j < i; ++j) {
@@ skipping 300 matching lines @@
   implicit_ref_groups_.Clear();
 }
 
 
 void GlobalHandles::TearDown() {
   // TODO(1428): invoke weak callbacks.
 }
 
 
 } }  // namespace v8::internal