Add UMA metric to track the time saved on making events passive before pageload

third_party/WebKit/Source/core/input/TouchEventManager.cpp

 // Copyright 2016 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 "core/input/TouchEventManager.h"
 
 #include "core/dom/Document.h"
 #include "core/events/TouchEvent.h"
 #include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/input/EventHandler.h"
 #include "core/input/TouchActionUtil.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "platform/Histogram.h"
 #include "platform/PlatformTouchEvent.h"
-
+#include "wtf/CurrentTime.h"
 
 
 namespace blink {
 
 namespace {
 
 bool hasTouchHandlers(const EventHandlerRegistry& registry)
 {
     return registry.hasEventHandlers(EventHandlerRegistry::TouchStartOrMoveEventBlocking)
         || registry.hasEventHandlers(EventHandlerRegistry::TouchStartOrMoveEventPassive)
@@ skipping 206 matching lines @@
                 event.getModifiers(), event.cancelable(), event.causesScrollingIfUncanceled(), event.timestamp());
 
             DispatchEventResult domDispatchResult = touchEventTarget->dispatchEvent(touchEvent);
 
             // Only report for top level documents with a single touch on
             // touch-start or the first touch-move.
             if (touchStartOrFirstTouchMove && touchInfos.size() == 1 && event.cancelable() && m_frame->isMainFrame()) {
                 DEFINE_STATIC_LOCAL(EnumerationHistogram, rootDocumentListenerHistogram, ("Event.Touch.TargetAndDispatchResult", TouchTargetAndDispatchResultTypeMax));
                 rootDocumentListenerHistogram.count(toTouchTargetHistogramValue(eventTarget, domDispatchResult));
 
-                // Count the handled touch starts and first touch moves before and after the page is fully loaded respectively.
+                // Count the handled touch starts and first touch moves before and after the page is fully loaded respectively and also their latency.

[tdresser, 2016/05/16 17:13:55]

Record the disposition and latency of touch starts and first...

[lanwei, 2016/05/16 20:23:09]

Done.

+                int64_t latencyInMicros = static_cast<int64_t>((currentTime() - event.timestamp()) * 1000000.0);
                 if (m_frame->document()->isLoadCompleted()) {
                     DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsAfterPageLoadHistogram, ("Event.Touch.TouchDispositionsAfterPageLoad", TouchEventDispatchResultTypeMax));
                     touchDispositionsAfterPageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+
+                    DEFINE_STATIC_LOCAL(CustomCountHistogram, eventLatencyAfterPageLoadHistogram, ("Event.Touch.TouchesAfterPageLoadLatency", 1, 10000000, 100));

[tdresser, 2016/05/16 17:13:55]

Let's bump up the maximum by a factor of 10. Right now it maxes out at 10
seconds, but we want to have some information about longer tasks.

[lanwei, 2016/05/16 20:23:09]

Done.

+                    eventLatencyAfterPageLoadHistogram.count(latencyInMicros);
                 } else {
                     DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsBeforePageLoadHistogram, ("Event.Touch.TouchDispositionsBeforePageLoad", TouchEventDispatchResultTypeMax));
                     touchDispositionsBeforePageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+
+                    DEFINE_STATIC_LOCAL(CustomCountHistogram, eventLatencyBeforePageLoadHistogram, ("Event.Touch.TouchesBeforePageLoadLatency", 1, 10000000, 100));
+                    eventLatencyBeforePageLoadHistogram.count(latencyInMicros);
                 }
             }
             eventResult = EventHandler::mergeEventResult(eventResult,
                 EventHandler::toWebInputEventResult(domDispatchResult));
         }
     }
     return eventResult;
 }
 
 void TouchEventManager::updateTargetAndRegionMapsForTouchStarts(
@@ skipping 255 matching lines @@
 }
 
 DEFINE_TRACE(TouchEventManager)
 {
     visitor->trace(m_frame);
     visitor->trace(m_touchSequenceDocument);
     visitor->trace(m_targetForTouchID);
 }
 
 } // namespace blink