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 811554176974f8afdcfe2a08b02ea5c5bb685d9b..8405e216412d0fba134318ac2317a7b2e8af5a2e 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -276,12 +276,13 @@ InputHandlerProxy::HandleInputEventWithLatencyInfo(
 
   std::unique_ptr<cc::SwapPromiseMonitor> latency_info_swap_promise_monitor =
       input_handler_->CreateLatencyInfoSwapPromiseMonitor(latency_info);
-  InputHandlerProxy::EventDisposition disposition = HandleInputEvent(event);
+  InputHandlerProxy::EventDisposition disposition =
+      HandleInputEvent(event, latency_info);
   return disposition;
 }
 
 InputHandlerProxy::EventDisposition InputHandlerProxy::HandleInputEvent(
-    const WebInputEvent& event) {
+    const WebInputEvent& event, ui::LatencyInfo* latency_info) {
   DCHECK(input_handler_);
 
   if (FilterInputEventForFlingBoosting(event))
@@ -297,7 +298,7 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleInputEvent(
 
     case WebInputEvent::GestureScrollUpdate:
       return HandleGestureScrollUpdate(
-          static_cast<const WebGestureEvent&>(event));
+          static_cast<const WebGestureEvent&>(event), latency_info);
 
     case WebInputEvent::GestureScrollEnd:
       return HandleGestureScrollEnd(static_cast<const WebGestureEvent&>(event));
@@ -647,7 +648,7 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleGestureScrollBegin(
 
 InputHandlerProxy::EventDisposition
 InputHandlerProxy::HandleGestureScrollUpdate(
-  const WebGestureEvent& gesture_event) {
+  const WebGestureEvent& gesture_event, ui::LatencyInfo* latency_info) {
 #ifndef NDEBUG
   DCHECK(expect_scroll_update_end_);
 #endif
@@ -662,8 +663,20 @@ InputHandlerProxy::HandleGestureScrollUpdate(
   if (ShouldAnimate(gesture_event.data.scrollUpdate.deltaUnits !=
                     blink::WebGestureEvent::ScrollUnits::Pixels)) {
     switch (input_handler_->ScrollAnimated(scroll_point, scroll_delta).thread) {
-      case cc::InputHandler::SCROLL_ON_IMPL_THREAD:
+      case cc::InputHandler::SCROLL_ON_IMPL_THREAD: {
+        for (const auto& lc : latency_info->latency_components()) {
+          if (lc.first.first == ui::INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT) {
+            LatencyInfo::LatencyComponent o_component;
+            if (latency_info->FindLatency(
+                ui::INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT, 0, &o_component)) {
+              input_handler_->AdjustDuration(
+                lc.second.event_time - o_component.event_time);

[skobes, 2016/06/08 22:47:28]

I don't really understand what this is doing, is it equivalent to using
WebInputEvent::timeStampSeconds?

+            }
+            break;
+          }
+        }
         return DID_HANDLE;
+      }
       case cc::InputHandler::SCROLL_IGNORED:
         return DROP_EVENT;
       default: