Add UMA metric to track the time saved on making events passive during fling

content/renderer/render_widget_unittest.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 "content/renderer/render_widget.h"
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/test/histogram_tester.h"
@@ skipping 309 matching lines @@
   EXPECT_CALL(*widget()->mock_webwidget(), handleInputEvent(_))
       .WillOnce(
           ::testing::Return(blink::WebInputEventResult::HandledApplication));
   touch.dispatchType = blink::WebInputEvent::DispatchType::Blocking;
   widget()->SendInputEvent(touch);
   histogram_tester().ExpectBucketCount(
       EVENT_LISTENER_RESULT_HISTOGRAM,
       PASSIVE_LISTENER_UMA_ENUM_CANCELABLE_AND_CANCELED, 1);
 }
 
+TEST_F(RenderWidgetUnittest, TouchStartDuringOrOutsideFlingUmaMetrics) {
+  EXPECT_CALL(*widget()->mock_webwidget(), handleInputEvent(_))
+      .Times(2)
+      .WillRepeatedly(
+          ::testing::Return(blink::WebInputEventResult::NotHandled));
+
+  SyntheticWebTouchEvent touch;
+  touch.PressPoint(10, 10);
+  touch.dispatchType = blink::WebInputEvent::DispatchType::Blocking;
+  touch.dispatchedDuringFling = true;
+  widget()->SendInputEvent(touch);
+  histogram_tester().ExpectTotalCount(
+      "Event.Touch.TouchStartDuringFlingLatency", 1);
+
+  touch.dispatchedDuringFling = false;
+  widget()->SendInputEvent(touch);
+  histogram_tester().ExpectTotalCount(
+      "Event.Touch.TouchStartOutsideFlingLatency", 1);
+}
+
 }  // namespace content