Move logic of recording main thread scrolling reasons from cc to blink::ScrollManager

ui/events/blink/input_handler_proxy.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 539 matching lines @@
       "Renderer4.MainThreadWheelScrollReason";
 
   DCHECK(device == blink::WebGestureDeviceTouchpad ||
          device == blink::WebGestureDeviceTouchscreen);
 
   if (device != blink::WebGestureDeviceTouchpad &&
       device != blink::WebGestureDeviceTouchscreen) {
     return;
   }
 
+  // NonCompositedScrollReasons should only be set on the main thread.
+  DCHECK(!cc::MainThreadScrollingReason::NonCompositedScrollReasons(reasons));

[bokan, 2017/04/07 17:39:03]

I think this check isn't what you want. The function currently currently means
(has any reason && all reasons are non-composited) so you're checking:

!(has any reason) || !(all reasons are non-composited)

Which is equivalent to:

No reasons || has some composited reasons

See my comment in NonCompositedScrollReasons() for how to address this.

[yigu, 2017/04/07 19:26:27]

Done.

+
   // UMA_HISTOGRAM_ENUMERATION requires that the enum_max must be strictly
   // greater than the sample value. kMainThreadScrollingReasonCount doesn't
   // include the NotScrollingOnMain enum but the histograms do so adding
   // the +1 is necessary.
   // TODO(dcheng): Fix https://crbug.com/705169 so this isn't needed.
   constexpr uint32_t kMainThreadScrollingReasonEnumMax =
       cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount + 1;
   if (reasons == cc::MainThreadScrollingReason::kNotScrollingOnMain) {
     if (device == blink::WebGestureDeviceTouchscreen) {
       UMA_HISTOGRAM_ENUMERATION(
@@ skipping 1072 matching lines @@
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 void InputHandlerProxy::SetTickClockForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   tick_clock_ = std::move(tick_clock);
 }
 
 }  // namespace ui