Ozone: Avoid blocking in Swapbuffer Call.

ui/ozone/platform/dri/gbm_surfaceless.cc

Index: ui/ozone/platform/dri/gbm_surfaceless.cc
diff --git a/ui/ozone/platform/dri/gbm_surfaceless.cc b/ui/ozone/platform/dri/gbm_surfaceless.cc
index b3748445a369b53d97866b759da0455c26cc4c0d..a6adb9edf084ba25d7eceed3e1b05f4731c522d0 100644
--- a/ui/ozone/platform/dri/gbm_surfaceless.cc
+++ b/ui/ozone/platform/dri/gbm_surfaceless.cc
@@ -8,11 +8,13 @@
 #include "ui/ozone/platform/dri/dri_window_delegate.h"
 #include "ui/ozone/platform/dri/gbm_buffer.h"
 #include "ui/ozone/platform/dri/hardware_display_controller.h"
+#include "ui/ozone/platform/dri/page_flip_event_handler.h"
 
 namespace ui {
 
-GbmSurfaceless::GbmSurfaceless(DriWindowDelegate* window_delegate)
-    : window_delegate_(window_delegate) {
+GbmSurfaceless::GbmSurfaceless(DriWindowDelegate* window_delegate,
+                               PageFlipEventHandler* handler)
+    : window_delegate_(window_delegate), flip_handler_(handler) {
 }
 
 GbmSurfaceless::~GbmSurfaceless() {}
@@ -33,7 +35,11 @@ bool GbmSurfaceless::OnSwapBuffers() {
     return true;
 
   bool success = controller->SchedulePageFlip();
-  controller->WaitForPageFlipEvent();
+
+  if (flip_handler_)
+    flip_handler_->GetPageFlipCompleted(controller, callback_);
+  else
+    controller->WaitForPageFlipEvent();
 
   return success;
 }
@@ -42,4 +48,9 @@ scoped_ptr<gfx::VSyncProvider> GbmSurfaceless::CreateVSyncProvider() {
   return scoped_ptr<gfx::VSyncProvider>(new DriVSyncProvider(window_delegate_));
 }
 
+void GbmSurfaceless::SetPageFlipCompletionCallback(
+    const PageFlipCompletionCallback& callback) {
+  callback_ = callback;
+}
+
 }  // namespace ui