Make shared memory segments writable only by their rightful owners.

BUG=143859
TEST=Chrome's UI still works on Linux and Chrome OS
Review URL: https://chromiumcodereview.appspot.com/10854242

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@158289 0039d316-1c4b-4281-b951-d872f2087c98
void XSyncHandler::PushPaintCounter(Display* display,
                                    Picture picture,
                                    Pixmap pixmap,
                                    const base::Closure& completion_callback) {
  backing_store_events_.push(
      new BackingStoreEvents(display, picture, pixmap, completion_callback));

  XSyncValue value;
  XSyncIntToValue(&value, 1);
  XSyncChangeCounter(ui::GetXDisplay(),
                     backing_store_sync_counter_,
                     value);
}

void XSyncHandler::PushPaintCounter(Display* display,
                                    Picture picture,
                                    Pixmap pixmap,
                                    const base::Closure& completion_callback) {
  backing_store_events_.push(
      new BackingStoreEvents(display, picture, pixmap, completion_callback));

  XSyncValue value;
  XSyncIntToValue(&value, 1);
  XSyncChangeCounter(ui::GetXDisplay(),
                     backing_store_sync_counter_,
                     value);
}
