[VSync Queue] Flush input in CommitComplete()

ui/events/blink/input_handler_proxy.cc

 // Copyright 2013 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 "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 307 matching lines @@
       !IsGestureScrollOrFlingOrPinch(event_with_callback->event().GetType())) {
     DispatchSingleInputEvent(std::move(event_with_callback),
                              tick_clock_->NowTicks());
     return;
   }
 
   if (has_ongoing_compositor_scroll_fling_pinch_) {
     bool needs_animate_input = compositor_event_queue_->empty();
     compositor_event_queue_->Queue(std::move(event_with_callback),
                                    tick_clock_->NowTicks());
+
+    if (input_handler_->GetInputHandlerState() ==
+        cc::InputHandler::InputHandlerState::IDLE) {
+      // Dispatch immediately to avoid checkerboard in high latency mode.
+      DispatchQueuedInputEvents();
+      return;
+    }
+
     if (needs_animate_input)
       input_handler_->SetNeedsAnimateInput();
     return;
   }
 
   // We have to dispatch the event to know whether the gesture sequence will be
   // handled by the compositor or not.
   DispatchSingleInputEvent(std::move(event_with_callback),
                            tick_clock_->NowTicks());
 }
@@ skipping 1307 matching lines @@
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 void InputHandlerProxy::SetTickClockForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   tick_clock_ = std::move(tick_clock);
 }
 
 }  // namespace ui