currentlyscrollinglayer cleared in scrollAnimatedBegin.

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 563 matching lines @@
   if (gesture_event.data.scrollBegin.deltaHintUnits ==
       blink::WebGestureEvent::ScrollUnits::Page) {
     scroll_status.thread = cc::InputHandler::SCROLL_ON_MAIN_THREAD;
     scroll_status.main_thread_scrolling_reasons =
         cc::MainThreadScrollingReason::kContinuingMainThreadScroll;
   } else if (gesture_event.data.scrollBegin.targetViewport) {
     scroll_status = input_handler_->RootScrollBegin(
         &scroll_state, GestureScrollInputType(gesture_event.sourceDevice));
   } else if (ShouldAnimate(gesture_event.data.scrollBegin.deltaHintUnits !=
                            blink::WebGestureEvent::ScrollUnits::Pixels)) {
+    DCHECK(!scroll_state.is_in_inertial_phase());
     gfx::Point scroll_point(gesture_event.x, gesture_event.y);
     scroll_status = input_handler_->ScrollAnimatedBegin(scroll_point);
   } else {
     scroll_status = input_handler_->ScrollBegin(
         &scroll_state, GestureScrollInputType(gesture_event.sourceDevice));
   }
   UMA_HISTOGRAM_ENUMERATION("Renderer4.CompositorScrollHitTestResult",
                             scroll_status.thread,
                             cc::InputHandler::LAST_SCROLL_STATUS + 1);
 
@@ skipping 743 matching lines @@
   // is made asynchronously, to minimize divergence between main thread and
   // impl thread event handling paths.
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(&InputScrollElasticityController::ObserveGestureEventAndResult,
                  scroll_elasticity_controller_->GetWeakPtr(), gesture_event,
                  scroll_result));
 }
 
 }  // namespace ui