Add UMA metric for tracking listeners for blocking touch before page finished loading

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

Index: third_party/WebKit/Source/core/input/EventHandler.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandler.cpp b/third_party/WebKit/Source/core/input/EventHandler.cpp
index 442b6da650562e5c4ac8773c60e462ed47e5999a..233379e2d45764b53adb92d25783aba6002aa1a3 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -3888,11 +3888,19 @@ WebInputEventResult EventHandler::dispatchTouchEvents(const PlatformTouchEvent&
 
             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->document()->ownerElement()) {
-                DEFINE_STATIC_LOCAL(EnumerationHistogram, rootDocumentListenerHistogram, ("Event.Touch.TargetAndDispatchResult", TouchTargetAndDispatchResultTypeMax));
-                rootDocumentListenerHistogram.count(toTouchTargetHistogramValue(eventTarget, domDispatchResult));
+            if (touchStartOrFirstTouchMove && touchInfos.size() == 1 && event.cancelable()) {
+                // Only report for top level documents with a single touch on
+                // touch-start or the first touch-move.
+                if (!m_frame->document()->ownerElement()) {
+                    DEFINE_STATIC_LOCAL(EnumerationHistogram, rootDocumentListenerHistogram, ("Event.Touch.TargetAndDispatchResult", TouchTargetAndDispatchResultTypeMax));
+                    rootDocumentListenerHistogram.count(toTouchTargetHistogramValue(eventTarget, domDispatchResult));
+                }
+
+                // Only count the canceled touch starts and first touch moves listener before page finishes loading.
+                if (!m_frame->document()->isLoadCompleted()) {
+                    DEFINE_STATIC_LOCAL(EnumerationHistogram, pageloadListenerHistogram, ("Event.Touch.TouchBlockingOnPageload", 2));

[dtapuska, 2016/04/22 17:34:14]

I'd prefer if these were called out as enums; as opposed to a magical 0, 1,
boolean.

[tdresser, 2016/04/22 17:34:52]

Let's have two histograms, once for before pageload, and once for after
pageload.

Event.Touch.TouchesCancelledBeforePageLoad
Event.Touch.TouchesCancelledAfterPageLoad

or something like that?

We should probably only be looking at cancelable touch events, right? Or we
should break the histogram up into more buckets, similar to what Dave has done.

[tdresser, 2016/04/22 17:37:06]

Sorry, missed the condition above that checked that we're only looking at
cancelable events.

[dtapuska, 2016/04/22 17:39:10]

How do we want to report this for iframes?

[tdresser, 2016/04/22 17:51:13]

I think we should only care about the top frame's document. It won't be
considered loaded until all subframes are loaded.

[dtapuska, 2016/04/22 18:02:35]

Right so the !m_frame->document()->ownerElement() should move back up to the top
if conditional.

+                    pageloadListenerHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? 1 : 0);
+                }
             }
             eventResult = mergeEventResult(eventResult, toWebInputEventResult(domDispatchResult));
         }