Respect the order of input messages from browser to renderer

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 6e9efe7da12de6f1c28011a48d2b0a4832cd7f00..c6c6a4991ced8372243e4604c61a3004ec987ccd 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -659,7 +659,8 @@ RenderViewImpl::RenderViewImpl(CompositorDependencies* compositor_deps,
       expected_content_intent_id_(0),
 #endif
       enumeration_completion_id_(0),
-      session_storage_namespace_id_(params.session_storage_namespace_id) {
+      session_storage_namespace_id_(params.session_storage_namespace_id),
+      has_added_input_handler_(false) {
   GetWidget()->set_owner_delegate(this);
 }
 
@@ -2051,17 +2052,19 @@ void RenderViewImpl::initializeLayerTreeView() {
   // (SnowLeopard, which has Aqua scrollbars which need synchronous updates).
   use_threaded_event_handling = compositor_deps_->IsElasticOverscrollEnabled();
 #endif
-  if (use_threaded_event_handling) {
-    RenderThreadImpl* render_thread = RenderThreadImpl::current();
-    // render_thread may be NULL in tests.
-    InputHandlerManager* input_handler_manager =
-        render_thread ? render_thread->input_handler_manager() : NULL;
-    if (input_handler_manager) {
-      input_handler_manager->AddInputHandler(
-          GetRoutingID(), rwc->GetInputHandler(), AsWeakPtr(),
-          webkit_preferences_.enable_scroll_animator,
-          UseGestureBasedWheelScrolling());
-    }
+  if (!use_threaded_event_handling)
+    return;
+
+  RenderThreadImpl* render_thread = RenderThreadImpl::current();
+  // render_thread may be NULL in tests.
+  InputHandlerManager* input_handler_manager =
+      render_thread ? render_thread->input_handler_manager() : NULL;
+  if (input_handler_manager) {
+    input_handler_manager->AddInputHandler(
+        GetRoutingID(), rwc->GetInputHandler(), AsWeakPtr(),
+        webkit_preferences_.enable_scroll_animator,
+        UseGestureBasedWheelScrolling());
+    has_added_input_handler_ = true;
   }
 }
 
@@ -2214,6 +2217,10 @@ float RenderViewImpl::GetDeviceScaleFactorForTest() const {
   return device_scale_factor_;
 }
 
+bool RenderViewImpl::HasAddedInputHandler() const {
+  return has_added_input_handler_;
+}
+
 gfx::Point RenderViewImpl::ConvertWindowPointToViewport(
     const gfx::Point& point) {
   blink::WebFloatRect point_in_viewport(point.x(), point.y(), 0, 0);