Add hooks for flushing input from BeginFrame dispatch on Aura

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 96cfc510dc14128fa6a06fa56334fd0c15fa7418..c992b8a4666ad33fe15e7c123c1926c05a703aed 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -15,6 +15,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/trace_event/trace_event.h"
+#include "cc/base/switches.h"
 #include "cc/layers/layer.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
@@ -473,9 +474,13 @@ RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host,
 #endif
       has_snapped_to_boundary_(false),
       is_guest_view_hack_(is_guest_view_hack),
-      begin_frame_observer_proxy_(this),
       set_focus_on_mouse_down_(false),
       weak_ptr_factory_(this) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          cc::switches::kEnableBeginFrameScheduling)) {
+    begin_frame_observer_proxy_.reset(new BeginFrameObserverProxy(this));
+  }
+
   if (!is_guest_view_hack_)
     host_->SetView(this);
 
@@ -742,10 +747,12 @@ ui::TextInputClient* RenderWidgetHostViewAura::GetTextInputClient() {
 }
 
 void RenderWidgetHostViewAura::OnSetNeedsBeginFrames(bool needs_begin_frames) {
-  begin_frame_observer_proxy_.SetNeedsBeginFrames(needs_begin_frames);
+  DCHECK(begin_frame_observer_proxy_);
+  begin_frame_observer_proxy_->SetNeedsBeginFrames(needs_begin_frames);
 }
 
 void RenderWidgetHostViewAura::SendBeginFrame(const cc::BeginFrameArgs& args) {
+  host_->FlushInput(args.frame_time);

[jdduke (slow), 2015/10/23 18:00:39]

In theory, we might want to be more refined about our dispatch here, discerning
between the cases where an input flush was requested and the renderer signaled a
need for BeginFrames. However, for V1 I think this is fine, eventually it'd be
nice if Aura/Android(/Mac?) used a similar subscription model.

   delegated_frame_host_->SetVSyncParameters(args.frame_time, args.interval);
   host_->Send(new ViewMsg_BeginFrame(host_->GetRoutingID(), args));
 }
@@ -1368,6 +1375,14 @@ InputEventAckState RenderWidgetHostViewAura::FilterInputEvent(
                   : INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
 }
 
+void RenderWidgetHostViewAura::OnSetNeedsFlushInput() {
+  if (begin_frame_observer_proxy_) {
+    begin_frame_observer_proxy_->SetNeedsOneBeginFrame();
+    return;
+  }
+  RenderWidgetHostViewBase::OnSetNeedsFlushInput();
+}
+
 BrowserAccessibilityManager*
 RenderWidgetHostViewAura::CreateBrowserAccessibilityManager(
     BrowserAccessibilityDelegate* delegate) {
@@ -2699,8 +2714,10 @@ void RenderWidgetHostViewAura::AddedToRootWindow() {
 #endif
 
   delegated_frame_host_->SetCompositor(window_->GetHost()->compositor());
-  if (window_->GetHost()->compositor())
-    begin_frame_observer_proxy_.SetCompositor(window_->GetHost()->compositor());
+  if (window_->GetHost()->compositor() && begin_frame_observer_proxy_) {
+    begin_frame_observer_proxy_->SetCompositor(
+        window_->GetHost()->compositor());
+  }
 }
 
 void RenderWidgetHostViewAura::RemovingFromRootWindow() {
@@ -2713,7 +2730,8 @@ void RenderWidgetHostViewAura::RemovingFromRootWindow() {
 
   window_->GetHost()->RemoveObserver(this);
   delegated_frame_host_->ResetCompositor();
-  begin_frame_observer_proxy_.ResetCompositor();
+  if (begin_frame_observer_proxy_)
+    begin_frame_observer_proxy_->ResetCompositor();
 
 #if defined(OS_WIN)
   // Update the legacy window's parent temporarily to the desktop window. It