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..e0884991d190c88b2038e5eed5f37faea8f6d3e8 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -256,6 +256,12 @@ TouchTargetAndDispatchResultType toTouchTargetHistogramValue(EventTarget* eventT
     return static_cast<TouchTargetAndDispatchResultType>(result);
 }
 
+enum TouchEventDispatchResultType {
+    NotHandledTouches, // Not handled touch events.
+    HandledTouches, // Handled touch events.
+    TouchEventDispatchResultTypeMax,
+};
+
 } // namespace
 
 using namespace HTMLNames;
@@ -3893,11 +3899,19 @@ WebInputEventResult EventHandler::dispatchTouchEvents(const PlatformTouchEvent&
             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));
+
+                // Count the cancelled touch starts and first touch moves before and after page finishes loading respectively.
+                if (m_frame->document()->isLoadCompleted()) {

[dtapuska, 2016/04/22 22:48:12]

Why can't this be a single histogram? Also canceled I believe is the preferred
US spelling; but best to do a grep to confirm. 

[lanwei, 2016/04/22 23:55:23]

I did a search of 'canceled' and 'cancelled', they occur 1,639 and 1,663 time in
the code respectively. You are right, in American English, it is one 'l'.

We can use one histogram, and have four different buckets. I do not know which
way is better. Tim, what do you think?

[tdresser, 2016/04/25 15:45:19]

It's somewhat easier to view a graph of the proportion that are cancelled
before/after pageload if we use two separate histograms.

The tools will now let us do this either way, but the tools will be simpler to
use if we split it up.

[dtapuska, 2016/04/25 19:49:09]

Two buckets seems fine to me. Inside blink source Canceled is used 240 times vs
Cancelled which is 107. Being that the 4 lines you add here it appears 2
different ways I'd prefer consistent and uses the US spelling.

[lanwei, 2016/04/25 20:29:34]

Done.

+                    DEFINE_STATIC_LOCAL(EnumerationHistogram, touchesCancelledAfterPageLoadHistogram, ("Event.Touch.TouchesCancelledAfterPageLoad", TouchEventDispatchResultTypeMax));
+                    touchesCancelledAfterPageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : NotHandledTouches);
+                } else {
+                    DEFINE_STATIC_LOCAL(EnumerationHistogram, touchesCancelledBeforePageLoadHistogram, ("Event.Touch.TouchesCancelledBeforePageLoad", TouchEventDispatchResultTypeMax));
+                    touchesCancelledBeforePageLoadHistogram.count((domDispatchResult != DispatchEventResult::NotCanceled) ? HandledTouches : NotHandledTouches);
+                }
             }
             eventResult = mergeEventResult(eventResult, toWebInputEventResult(domDispatchResult));
         }
     }
-
     return eventResult;
 }