Fix recording of kAnimatingScrollOnMain

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 409 matching lines @@
           cc::MainThreadScrollingReason::kNotScrollingOnMain,
           cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount);
     }
   }
 
   for (uint32_t i = 0;
        i < cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount - 1;
        ++i) {
     unsigned val = 1 << i;
     if (reasons & val) {
+      if (val == cc::MainThreadScrollingReason::kAnimatingScrollOnMainThread) {
+        // We only want to record "animating scroll on main thread" reason if
+        // it's the only reason. Bail if that's not the case.
+        if (reasons & ~val)
+          continue;
+      }
       if (device == blink::WebGestureDeviceTouchscreen) {
         UMA_HISTOGRAM_ENUMERATION(
             kGestureHistogramName, i + 1,
             cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount);
       } else {
         UMA_HISTOGRAM_ENUMERATION(
             kWheelHistogramName, i + 1,
             cc::MainThreadScrollingReason::kMainThreadScrollingReasonCount);
       }
     }
@@ skipping 889 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