Take MT jank into account when animating the scroll offset on CC

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index 1d4a119420bbfc7103437d70a83da022085c87af..d68605c139187a63e976e3bfc9301331915e39f8 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -493,7 +493,7 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::ScrollByMouseWheel(
   } else if (ShouldAnimate(wheel_event.hasPreciseScrollingDeltas)) {
     cc::InputHandler::ScrollStatus scroll_status =
         input_handler_->ScrollAnimated(gfx::Point(wheel_event.x, wheel_event.y),
-                                       scroll_delta);
+                                       scroll_delta, base::TimeDelta());
 
     RecordMainThreadScrollingReasons(
         blink::WebGestureDeviceTouchpad,
@@ -625,7 +625,7 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleGestureScrollBegin(
 
 InputHandlerProxy::EventDisposition
 InputHandlerProxy::HandleGestureScrollUpdate(
-  const WebGestureEvent& gesture_event) {
+    const WebGestureEvent& gesture_event) {
 #ifndef NDEBUG
   DCHECK(expect_scroll_update_end_);
 #endif
@@ -639,7 +639,12 @@ InputHandlerProxy::HandleGestureScrollUpdate(
 
   if (ShouldAnimate(gesture_event.data.scrollUpdate.deltaUnits !=
                     blink::WebGestureEvent::ScrollUnits::Pixels)) {
-    switch (input_handler_->ScrollAnimated(scroll_point, scroll_delta).thread) {
+    base::TimeDelta delay =
+        (base::TimeTicks::Now() -
+         (base::TimeTicks() +
+          base::TimeDelta::FromSecondsD(gesture_event.timeStampSeconds)));

[tdresser, 2016/08/25 15:55:54]

Math seems correct, though I might add a temporary here to make this prettier.

[ymalik, 2016/08/29 14:52:06]

Good tip, looks much prettier!

+    switch (input_handler_->ScrollAnimated(scroll_point, scroll_delta, delay)
+                .thread) {
       case cc::InputHandler::SCROLL_ON_IMPL_THREAD:
         return DID_HANDLE;
       case cc::InputHandler::SCROLL_IGNORED: