[Ozone-DRI] Fix waiting for page flips in mirror mode

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 716ec383a5231d39f99c1fccba951486cf83d0cd..ee4e4a94626adf892b35a605a2b22e1ee7a540d2 100644
--- a/ui/ozone/platform/dri/hardware_display_controller.cc
+++ b/ui/ozone/platform/dri/hardware_display_controller.cc
@@ -119,7 +119,10 @@ void HardwareDisplayController::WaitForPageFlipEvent() {
   bool has_pending_page_flips = false;
   // Wait for the page-flips to complete.
   for (size_t i = 0; i < crtc_controllers_.size(); ++i) {
-    if (crtc_controllers_[i]->page_flip_pending()) {
+    // 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);
     }