PPAPI: Force async callback invocation option.

ppapi/cpp/paint_manager.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/cpp/paint_manager.h"
 
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/cpp/instance.h"
 #include "ppapi/cpp/logging.h"
 #include "ppapi/cpp/module.h"
@@ skipping 135 matching lines @@
     pending_size_ = Size();
   }
 
   // Apply any scroll before asking the client to paint.
   if (update.has_scroll)
     graphics_.Scroll(update.scroll_rect, update.scroll_delta);
 
   if (client_->OnPaint(graphics_, update.paint_rects, update.paint_bounds)) {
     // Something was painted, schedule a flush.
     int32_t result = graphics_.Flush(
-        callback_factory_.NewCallback(&PaintManager::OnFlushComplete));
+        callback_factory_.NewOptionalCallback(&PaintManager::OnFlushComplete));
 
     // If you trigger this assertion, then your plugin has called Flush()
     // manually. When using the PaintManager, you should not call Flush, it
     // will handle that for you because it needs to know when it can do the
     // next paint by implementing the flush callback.
     //
     // Another possible cause of this assertion is re-using devices. If you
     // use one device, swap it with another, then swap it back, we won't know
     // that we've already scheduled a Flush on the first device. It's best to
     // not re-use devices in this way.
@@ skipping 27 matching lines @@
   // Just because we have a manual callback doesn't mean there are actually any
   // invalid regions. Even though we only schedule this callback when something
   // is pending, a Flush callback could have come in before this callback was
   // executed and that could have cleared the queue.
   if (aggregator_.HasPendingUpdate() && !flush_pending_)
     DoPaint();
 }
 
 
 }  // namespace pp