Ozone: Avoid blocking in Swapbuffer Call.

ui/ozone/platform/dri/hardware_display_controller.cc

Index: ui/ozone/platform/dri/hardware_display_controller.cc
diff --git a/ui/ozone/platform/dri/hardware_display_controller.cc b/ui/ozone/platform/dri/hardware_display_controller.cc
index 054e726a4474cf0542c6d1421e695c705969e445..f0b88bb5922c63da19cdd7e824de3cb729618695 100644
--- a/ui/ozone/platform/dri/hardware_display_controller.cc
+++ b/ui/ozone/platform/dri/hardware_display_controller.cc
@@ -105,6 +105,9 @@ bool HardwareDisplayController::SchedulePageFlip() {
   for (size_t i = 0; i < crtc_controllers_.size(); ++i)
     status &= crtc_controllers_[i]->SchedulePageFlip(pending_planes_);
 
+  current_planes_.swap(pending_planes_);
+  pending_planes_.clear();
+
   return status;
 }
 
@@ -116,24 +119,15 @@ void HardwareDisplayController::WaitForPageFlipEvent() {
   drm_event.page_flip_handler = HandlePageFlipEvent;
   drm_event.vblank_handler = NULL;
 
-  bool has_pending_page_flips = false;
   // Wait for the page-flips to complete.
   for (size_t i = 0; i < crtc_controllers_.size(); ++i) {
     // In mirror mode the page flip callbacks can happen in different order than
     // scheduled, so we need to make sure that the event for the current CRTC is
     // processed before moving to the next CRTC.
     while (crtc_controllers_[i]->page_flip_pending()) {
-      has_pending_page_flips = true;
       crtc_controllers_[i]->drm()->HandleEvent(drm_event);
     }
   }
-
-  // In case there are no pending pageflips do not replace the current planes
-  // since they are still being used.
-  if (has_pending_page_flips)
-    current_planes_.swap(pending_planes_);
-
-  pending_planes_.clear();
 }
 
 bool HardwareDisplayController::SetCursor(