Make first TouchStart and first TouchMove events on a flinging layer non-blocking

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/Deprecation.h"
 #include "core/frame/EventHandlerRegistry.h"
@@ skipping 174 matching lines @@
             EventTarget* touchEventTarget = eventTarget;
             TouchEvent* touchEvent = TouchEvent::create(
                 touches, touchesByTarget.get(touchEventTarget), changedTouches[state].m_touches.get(),
                 eventName, touchEventTarget->toNode()->document().domWindow(),
                 event.getModifiers(), event.cancelable(), event.causesScrollingIfUncanceled(), touchStartOrFirstTouchMove, 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()) {
+            if (touchStartOrFirstTouchMove && touchInfos.size() == 1 && m_frame->isMainFrame()) {
 
                 // Record the disposition and latency of touch starts and first touch moves before and after the page is fully loaded respectively.
                 int64_t latencyInMicros = static_cast<int64_t>((monotonicallyIncreasingTime() - 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);
+                if (event.cancelable()) {
+                    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.TouchLatencyAfterPageLoad", 1, 100000000, 50));
-                    eventLatencyAfterPageLoadHistogram.count(latencyInMicros);
-                } else {
-                    DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsBeforePageLoadHistogram, ("Event.Touch.TouchDispositionsBeforePageLoad", TouchEventDispatchResultTypeMax));
-                    touchDispositionsBeforePageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
+                        DEFINE_STATIC_LOCAL(CustomCountHistogram, eventLatencyAfterPageLoadHistogram, ("Event.Touch.TouchLatencyAfterPageLoad", 1, 100000000, 50));
+                        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.TouchLatencyBeforePageLoad", 1, 100000000, 50));
-                    eventLatencyBeforePageLoadHistogram.count(latencyInMicros);
+                        DEFINE_STATIC_LOCAL(CustomCountHistogram, eventLatencyBeforePageLoadHistogram, ("Event.Touch.TouchLatencyBeforePageLoad", 1, 100000000, 50));
+                        eventLatencyBeforePageLoadHistogram.count(latencyInMicros);
+                    }
                 }
 
                 // Report the touch disposition, split by whether there is an active fling animation.
-                if (event.type() == PlatformEvent::TouchStart) {
-                    if (event.dispatchedDuringFling()) {
-                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsDuringFlingHistogram, ("Event.Touch.TouchDispositionsDuringFling", TouchEventDispatchResultTypeMax));
+                if (event.dispatchedDuringFling()) {
+                    if (event.dispatchType() == PlatformEvent::ListenersForcedNonBlockingPassiveDueToFling) {
+                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsDuringFlingHistogram, ("Event.Touch.TouchDispositionsDuringFling2", TouchEventDispatchResultTypeMax));

[dtapuska, 2016/08/10 14:47:42]

if it is forced to be non blocking then it will always be not handled won't it.
because you can't prevent default it?

we might need a uma metric to track how many times preventDefault was called
inside a intervened event; that may be a useful metric. I'm not sure this is
really caturing that.

                         touchDispositionsDuringFlingHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
-                    } else {
-                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsOutsideFlingHistogram, ("Event.Touch.TouchDispositionsOutsideFling", TouchEventDispatchResultTypeMax));
+                    }
+                } else {
+                    if (event.cancelable()) {
+                        DEFINE_STATIC_LOCAL(EnumerationHistogram, touchDispositionsOutsideFlingHistogram, ("Event.Touch.TouchDispositionsOutsideFling2", TouchEventDispatchResultTypeMax));
                         touchDispositionsOutsideFlingHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : UnhandledTouches);
                     }
                 }
             }
             eventResult = EventHandler::mergeEventResult(eventResult,
                 EventHandler::toWebInputEventResult(domDispatchResult));
         }
     }
 
     if (allTouchesReleased)
@@ skipping 303 matching lines @@
         feature = UseCounter::TouchEndDuringScrollUserGestureUtilized;
         break;
     default:
         NOTREACHED();
         return;
     }
     Deprecation::countDeprecation(m_frame, feature);
 }
 
 } // namespace blink