Flush the pending input ack when the RenderWidget is hidden

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 791943acaa955fb56bec231f3b6276f05bb572f6..3b618dc8f6051b1149e30647c923abb61eba4066 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -1760,8 +1760,11 @@ 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