Ozone: Avoid blocking in Swapbuffer Call.

ui/ozone/platform/dri/gbm_surfaceless.h

Index: ui/ozone/platform/dri/gbm_surfaceless.h
diff --git a/ui/ozone/platform/dri/gbm_surfaceless.h b/ui/ozone/platform/dri/gbm_surfaceless.h
index dd755e41c9a50b16932c7d9349db88112e4a8371..c7129ddcbea36b252b6e0eda0886d3aa623106f9 100644
--- a/ui/ozone/platform/dri/gbm_surfaceless.h
+++ b/ui/ozone/platform/dri/gbm_surfaceless.h
@@ -14,6 +14,7 @@ class Size;
 namespace ui {
 
 class DriWindowDelegate;
+class PageFlipEventHandler;
 
 // In surfaceless mode drawing and displaying happens directly through
 // NativePixmap buffers. CC would call into SurfaceFactoryOzone to allocate the
@@ -21,7 +22,8 @@ class DriWindowDelegate;
 // presentation.
 class GbmSurfaceless : public SurfaceOzoneEGL {
  public:
-  GbmSurfaceless(DriWindowDelegate* window_delegate);
+  GbmSurfaceless(DriWindowDelegate* window_delegate,
+                 PageFlipEventHandler* handler = NULL);
   ~GbmSurfaceless() override;
 
   // SurfaceOzoneEGL:
@@ -29,9 +31,13 @@ class GbmSurfaceless : public SurfaceOzoneEGL {
   bool ResizeNativeWindow(const gfx::Size& viewport_size) override;
   bool OnSwapBuffers() override;
   scoped_ptr<gfx::VSyncProvider> CreateVSyncProvider() override;
+  void SetPageFlipCompletionCallback(
+      const PageFlipCompletionCallback& callback) override;
 
  protected:
   DriWindowDelegate* window_delegate_;
+  PageFlipEventHandler* flip_handler_;  // Not owned.
+  PageFlipCompletionCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(GbmSurfaceless);
 };