[Android] Provide synchronized input flush with BeginFrame

content/browser/renderer_host/render_widget_host_view_android.cc

Index: content/browser/renderer_host/render_widget_host_view_android.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_android.cc b/content/browser/renderer_host/render_widget_host_view_android.cc
index 5ebd7d4aa4abe33eb51cf17a795964d120d129bd..2731e002086dd95be0a933dc2a4841b43ff91ab5 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -114,7 +114,8 @@ RenderWidgetHostViewAndroid::RenderWidgetHostViewAndroid(
       texture_id_in_layer_(0),
       current_mailbox_output_surface_id_(kUndefinedOutputSurfaceId),
       weak_ptr_factory_(this),
-      overscroll_effect_enabled_(true) {
+      overscroll_effect_enabled_(true),
+      flush_input_requested_(false) {
   if (CompositorImpl::UsesDirectGL()) {
     surface_texture_transport_.reset(new SurfaceTextureTransportClient());
     layer_ = surface_texture_transport_->Initialize();
@@ -460,8 +461,16 @@ void RenderWidgetHostViewAndroid::OnDidChangeBodyBackgroundColor(
 void RenderWidgetHostViewAndroid::SendBeginFrame(
     const cc::BeginFrameArgs& args) {
   TRACE_EVENT0("cc", "RenderWidgetHostViewAndroid::SendBeginFrame");
-  if (host_)
-    host_->Send(new ViewMsg_BeginFrame(host_->GetRoutingID(), args));
+  if (!host_)
+    return;
+
+  if (flush_input_requested_) {
+    flush_input_requested_ = false;
+    host_->FlushInput();
+    content_view_core_->RemoveBeginFrameSubscriber();
+  }
+
+  host_->Send(new ViewMsg_BeginFrame(host_->GetRoutingID(), args));
 }
 
 void RenderWidgetHostViewAndroid::OnSetNeedsBeginFrame(
@@ -469,10 +478,14 @@ void RenderWidgetHostViewAndroid::OnSetNeedsBeginFrame(
   TRACE_EVENT1("cc", "RenderWidgetHostViewAndroid::OnSetNeedsBeginFrame",
                "enabled", enabled);
   // ContentViewCoreImpl handles multiple subscribers to the BeginFrame, so
-  // we have to make sure calls to ContentViewCoreImpl's SetNeedsBeginFrame
-  // are balanced, even if RenderWidgetHostViewAndroid's may not be.
+  // we have to make sure calls to ContentViewCoreImpl's
+  // {Add,Remove}BeginFrameSubscriber are balanced, even if
+  // RenderWidgetHostViewAndroid's may not be.
   if (content_view_core_ && needs_begin_frame_ != enabled) {
-    content_view_core_->SetNeedsBeginFrame(enabled);
+    if (enabled)
+      content_view_core_->AddBeginFrameSubscriber();
+    else
+      content_view_core_->RemoveBeginFrameSubscriber();
     needs_begin_frame_ = enabled;
   }
 }
@@ -971,6 +984,13 @@ InputEventAckState RenderWidgetHostViewAndroid::FilterInputEvent(
   return INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
 }
 
+void RenderWidgetHostViewAndroid::OnSetNeedsFlushInput() {
+  if (flush_input_requested_ || !content_view_core_)
+    return;
+  flush_input_requested_ = true;
+  content_view_core_->AddBeginFrameSubscriber();
+}
+
 void RenderWidgetHostViewAndroid::OnAccessibilityEvents(
     const std::vector<AccessibilityHostMsg_EventParams>& params) {
   if (!host_ ||