Add hooks for flushing input from BeginFrame dispatch on Aura

content/browser/renderer_host/begin_frame_observer_proxy.cc

 // Copyright 2015 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/browser/renderer_host/begin_frame_observer_proxy.h"
 
 namespace content {
 
 BeginFrameObserverProxy::BeginFrameObserverProxy(
     BeginFrameObserverProxyClient* client)
     : needs_begin_frames_(false),
+      needs_one_begin_frame_(false),
+      observing_begin_frames_(false),
       client_(client),
-      compositor_(nullptr) {
-}
+      compositor_(nullptr) {}
 
 BeginFrameObserverProxy::~BeginFrameObserverProxy() {
   DCHECK(!compositor_);
 }
 
 void BeginFrameObserverProxy::SetNeedsBeginFrames(bool needs_begin_frames) {
   if (needs_begin_frames_ == needs_begin_frames)
     return;
 
   needs_begin_frames_ = needs_begin_frames;
+  UpdateBeginFrameObservation();
+}
 
-  // In some cases, BeginFrame message is requested before |client_|'s window is
-  // added in the root window hierarchy.
-  if (!compositor_)
+void BeginFrameObserverProxy::SetNeedsOneBeginFrame() {
+  if (needs_one_begin_frame_)
     return;
 
-  if (needs_begin_frames)
-    StartObservingBeginFrames();
-  else
-    StopObservingBeginFrames();
+  needs_one_begin_frame_ = true;
+  UpdateBeginFrameObservation();
 }
 
 void BeginFrameObserverProxy::SetCompositor(ui::Compositor* compositor) {
   DCHECK(!compositor_);
   DCHECK(compositor);
 
   compositor_ = compositor;
   compositor_->AddObserver(this);
-  if (needs_begin_frames_)
-    StartObservingBeginFrames();
+  UpdateBeginFrameObservation();
 }
 
 void BeginFrameObserverProxy::ResetCompositor() {
   if (!compositor_)
     return;
   compositor_->RemoveObserver(this);
-
-  if (needs_begin_frames_)
-    StopObservingBeginFrames();
+  StopObservingBeginFrames();
   compositor_ = nullptr;
 }
 
 void BeginFrameObserverProxy::OnSendBeginFrame(const cc::BeginFrameArgs& args) {
-  if (last_sent_begin_frame_args_.frame_time != args.frame_time)
+  DCHECK(needs_one_begin_frame_ || needs_begin_frames_);
+  if (last_sent_begin_frame_args_.frame_time != args.frame_time) {
+    // Don't immediately unsubscribe in case BeginFrame dispatch triggers
+    // another request.
+    needs_one_begin_frame_ = false;
     client_->SendBeginFrame(args);
+    UpdateBeginFrameObservation();
+  }
   last_sent_begin_frame_args_ = args;
 }
 
 void BeginFrameObserverProxy::OnCompositingShuttingDown(
     ui::Compositor* compositor) {
   ResetCompositor();
 }
 
+void BeginFrameObserverProxy::UpdateBeginFrameObservation() {
+  // In some cases, BeginFrame message is requested before |client_|'s window is
+  // added in the root window hierarchy.
+  if (!compositor_) {
+    DCHECK(!observing_begin_frames_);
+    return;
+  }
+
+  if (needs_begin_frames_ || needs_one_begin_frame_)
+    StartObservingBeginFrames();
+  else
+    StopObservingBeginFrames();
+}
+
 void BeginFrameObserverProxy::StartObservingBeginFrames() {
   DCHECK(compositor_);
-  compositor_->AddBeginFrameObserver(this);
+  if (!observing_begin_frames_) {
+    observing_begin_frames_ = true;
+    compositor_->AddBeginFrameObserver(this);
+  }
 }
 
 void BeginFrameObserverProxy::StopObservingBeginFrames() {
   DCHECK(compositor_);
-  compositor_->RemoveBeginFrameObserver(this);
+  if (observing_begin_frames_) {
+    observing_begin_frames_ = false;
+    compositor_->RemoveBeginFrameObserver(this);
+  }
 }
 
 }  // namespace content