Fixes Windows build bots.

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 3570 matching lines @@
   Address block_address = p->area_start();
 
   // Skip over all the dead objects at the start of the page and mark them free.
   for (;
        cell_index < last_cell_index;
        cell_index++, block_address += 32 * kPointerSize) {
     if (cells[cell_index] != 0) break;
   }
   size_t size = block_address - p->area_start();
   if (cell_index == last_cell_index) {
-    freed_bytes += Free<mode>(space, free_list, p->area_start(), size);
+    freed_bytes += Free<mode>(space, free_list, p->area_start(),
+                              static_cast<int>(size));
     ASSERT_EQ(0, p->LiveBytes());
     return freed_bytes;
   }
   // Grow the size of the start-of-page free space a little to get up to the
   // first live object.
   Address free_end = StartOfLiveObject(block_address, cells[cell_index]);
   // Free the first free space.
   size = free_end - p->area_start();
-  freed_bytes += Free<mode>(space, free_list, p->area_start(), size);
+  freed_bytes += Free<mode>(space, free_list, p->area_start(),
+                            static_cast<int>(size));
 
   // The start of the current free area is represented in undigested form by
   // the address of the last 32-word section that contained a live object and
   // the marking bitmap for that cell, which describes where the live object
   // started.  Unless we find a large free space in the bitmap we will not
   // digest this pair into a real address.  We start the iteration here at the
   // first word in the marking bit map that indicates a live object.
   Address free_start = block_address;
   uint32_t free_start_cell = cells[cell_index];
 
@@ skipping 404 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal