Build error fix after r14283.

src/mark-compact.cc

 // Copyright 2012 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 1930 matching lines @@
     return;
 
   ref_groups->Sort();
   representative_objects->Sort();
 
   int surviving_ref_group_index = 0;
   int surviving_representative_object_index = 0;
 
   int representative_objects_index = 0;
   UniqueId current_group_id(0);
-  size_t current_group_start = 0;
+  int current_group_start = 0;
   for (int i = 0; i <= ref_groups->length(); ++i) {
     if (i == 0)
       current_group_id = ref_groups->at(i).id;
     if (i == ref_groups->length() || current_group_id != ref_groups->at(i).id) {
       // Group detected: objects in indices [current_group_start, i[.
 
       // Find the representative object for this group.
       while (representative_objects_index < representative_objects->length() &&
              representative_objects->at(representative_objects_index).id <
              current_group_id)
@@ skipping 2207 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal