Flush the pending input ack when the RenderWidget is hidden

content/renderer/render_widget.cc

 // Copyright (c) 2012 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 "content/renderer/render_widget.h"
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 1742 matching lines @@
 
 gfx::Vector2d RenderWidget::GetScrollOffset() {
   // Bare RenderWidgets don't support scroll offset.
   return gfx::Vector2d();
 }
 
 void RenderWidget::SetHidden(bool hidden) {
   if (is_hidden_ == hidden)
     return;
 
-  // The status has changed.  Tell the RenderThread about it.
+  // The status has changed.  Tell the RenderThread about it and ensure
+  // throttled acks are released in case frame production ceases.
   is_hidden_ = hidden;
+  FlushPendingInputEventAck();
+
   if (is_hidden_)
     RenderThreadImpl::current()->WidgetHidden();
   else
     RenderThreadImpl::current()->WidgetRestored();
 }
 
 void RenderWidget::WillToggleFullscreen() {
   if (!webwidget_)
     return;
 
@@ skipping 591 matching lines @@
 void RenderWidget::RegisterVideoHoleFrame(RenderFrameImpl* frame) {
   video_hole_frames_.AddObserver(frame);
 }
 
 void RenderWidget::UnregisterVideoHoleFrame(RenderFrameImpl* frame) {
   video_hole_frames_.RemoveObserver(frame);
 }
 #endif  // defined(VIDEO_HOLE)
 
 }  // namespace content