Add UMA metric for tracking root level listeners for blocking touch.

third_party/WebKit/Source/core/events/TouchEvent.cpp

Index: third_party/WebKit/Source/core/events/TouchEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/TouchEvent.cpp b/third_party/WebKit/Source/core/events/TouchEvent.cpp
index 721ec81f34e7ac66bfebdc6348c896a6b6a0f4ac..8a31f4f2142c39c8996628ef9425c912c6f10ee4 100644
--- a/third_party/WebKit/Source/core/events/TouchEvent.cpp
+++ b/third_party/WebKit/Source/core/events/TouchEvent.cpp
@@ -30,11 +30,123 @@
 #include "bindings/core/v8/ScriptState.h"
 #include "core/events/EventDispatcher.h"
 #include "core/frame/FrameConsole.h"
+#include "core/frame/FrameView.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/inspector/ConsoleMessage.h"
+#include "platform/Histogram.h"
 
 namespace blink {
 
+namespace {
+
+// These offsets change indicies into the ListenerHistogram

[Rick Byers, 2016/05/18 18:37:18]

this is quite a lot of complexity / details.  Talking with you and Tim I agree
this is worthwhile in figuring out our touch scroll intervention, but once we've
got that figured out we should probably remove all this.  To make that clear
please add a TODO comment saying to remove this once http://crbug.com/599609 is
fixed.

[dtapuska, 2016/05/19 16:11:21]

Done.

+// enumeration. The addition of a series of offsets then
+// produces the resulting ListenerHistogram value.
+const size_t kTouchTargetHistogramRootScrollerOffset = 6;
+const size_t kTouchTargetHistogramScrollableDocumentOffset = 3;
+const size_t kTouchTargetHistogramAlreadyHandledOffset = 0;
+const size_t kTouchTargetHistogramNotHandledOffset = 1;
+const size_t kTouchTargetHistogramHandledOffset = 2;
+const size_t kCapturingOffset = 0;
+const size_t kAtTargetOffset = 12;
+const size_t kBubblingOffset = 24;
+
+enum TouchTargetAndDispatchResultType {
+    // The following enums represent state captured during the CAPTURING_PHASE.
+    CapturingNonRootScrollerNonScrollableAlreadyHandled, // Non-root-scroller, non-scrollable document, already handled.
+    CapturingNonRootScrollerNonScrollableNotHandled, // Non-root-scroller, non-scrollable document, not handled.
+    CapturingNonRootScrollerNonScrollableHandled, // Non-root-scroller, non-scrollable document, handled application.
+    CapturingNonRootScrollerScrollableDocumentAlreadyHandled, // Non-root-scroller, scrollable document, already handled.
+    CapturingNonRootScrollerScrollableDocumentNotHandled, // Non-root-scroller, scrollable document, not handled.
+    CapturingNonRootScrollerScrollableDocumentHandled, // Non-root-scroller, scrollable document, handled application.
+    CapturingRootScrollerNonScrollableAlreadyHandled, // Root-scroller, non-scrollable document, already handled.
+    CapturingRootScrollerNonScrollableNotHandled, // Root-scroller, non-scrollable document, not handled.
+    CapturingRootScrollerNonScrollableHandled, // Root-scroller, non-scrollable document, handled.
+    CapturingRootScrollerScrollableDocumentAlreadyHandled, // Root-scroller, scrollable document, already handled.
+    CapturingRootScrollerScrollableDocumentNotHandled, // Root-scroller, scrollable document, not handled.
+    CapturingRootScrollerScrollableDocumentHandled, // Root-scroller, scrollable document, handled.
+
+    // The following enums represent state captured during the AT_TARGET phase.
+    NonRootScrollerNonScrollableAlreadyHandled, // Non-root-scroller, non-scrollable document, already handled.
+    NonRootScrollerNonScrollableNotHandled, // Non-root-scroller, non-scrollable document, not handled.
+    NonRootScrollerNonScrollableHandled, // Non-root-scroller, non-scrollable document, handled application.
+    NonRootScrollerScrollableDocumentAlreadyHandled, // Non-root-scroller, scrollable document, already handled.
+    NonRootScrollerScrollableDocumentNotHandled, // Non-root-scroller, scrollable document, not handled.
+    NonRootScrollerScrollableDocumentHandled, // Non-root-scroller, scrollable document, handled application.
+    RootScrollerNonScrollableAlreadyHandled, // Root-scroller, non-scrollable document, already handled.
+    RootScrollerNonScrollableNotHandled, // Root-scroller, non-scrollable document, not handled.
+    RootScrollerNonScrollableHandled, // Root-scroller, non-scrollable document, handled.
+    RootScrollerScrollableDocumentAlreadyHandled, // Root-scroller, scrollable document, already handled.
+    RootScrollerScrollableDocumentNotHandled, // Root-scroller, scrollable document, not handled.
+    RootScrollerScrollableDocumentHandled, // Root-scroller, scrollable document, handled.
+
+    // The following enums represent state captured during the BUBBLING_PHASE.
+    BubblingNonRootScrollerNonScrollableAlreadyHandled, // Non-root-scroller, non-scrollable document, already handled.
+    BubblingNonRootScrollerNonScrollableNotHandled, // Non-root-scroller, non-scrollable document, not handled.
+    BubblingNonRootScrollerNonScrollableHandled, // Non-root-scroller, non-scrollable document, handled application.
+    BubblingNonRootScrollerScrollableDocumentAlreadyHandled, // Non-root-scroller, scrollable document, already handled.
+    BubblingNonRootScrollerScrollableDocumentNotHandled, // Non-root-scroller, scrollable document, not handled.
+    BubblingNonRootScrollerScrollableDocumentHandled, // Non-root-scroller, scrollable document, handled application.
+    BubblingRootScrollerNonScrollableAlreadyHandled, // Root-scroller, non-scrollable document, already handled.
+    BubblingRootScrollerNonScrollableNotHandled, // Root-scroller, non-scrollable document, not handled.
+    BubblingRootScrollerNonScrollableHandled, // Root-scroller, non-scrollable document, handled.
+    BubblingRootScrollerScrollableDocumentAlreadyHandled, // Root-scroller, scrollable document, already handled.
+    BubblingRootScrollerScrollableDocumentNotHandled, // Root-scroller, scrollable document, not handled.
+    BubblingRootScrollerScrollableDocumentHandled, // Root-scroller, scrollable document, handled.
+    TouchTargetAndDispatchResultTypeMax,
+};
+
+void logTouchTargetHistogram(EventTarget* eventTarget, unsigned short phase, bool defaultPreventedBeforeCurrentTarget, bool defaultPrevented)
+{
+    int result = 0;
+    Document* document = nullptr;
+
+    switch (phase) {
+    default:
+    case Event::NONE:
+        return;
+    case Event::CAPTURING_PHASE:
+        result += kCapturingOffset;
+        break;
+    case Event::AT_TARGET:
+        result += kAtTargetOffset;
+        break;
+    case Event::BUBBLING_PHASE:
+        result += kBubblingOffset;
+        break;
+    }
+
+    if (const LocalDOMWindow* domWindow = eventTarget->toLocalDOMWindow()) {
+        // Treat the window as a root scroller as well.
+        document = domWindow->document();
+        result += kTouchTargetHistogramRootScrollerOffset;
+    } else if (Node* node = eventTarget->toNode()) {
+        // Report if the target node is the document or body.
+        if (node->isDocumentNode() || node->document().documentElement() == node || node->document().body() == node) {
+            result += kTouchTargetHistogramRootScrollerOffset;
+        }
+        document = &node->document();
+    }
+
+    if (document) {
+        FrameView* view = document->view();
+        if (view && view->isScrollable())
+            result += kTouchTargetHistogramScrollableDocumentOffset;
+    }
+
+    if (defaultPreventedBeforeCurrentTarget)
+        result += kTouchTargetHistogramAlreadyHandledOffset;
+    else if (defaultPrevented)
+        result += kTouchTargetHistogramHandledOffset;
+    else
+        result += kTouchTargetHistogramNotHandledOffset;
+
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, rootDocumentListenerHistogram, ("Event.Touch.TargetAndDispatchResult2", TouchTargetAndDispatchResultTypeMax));
+    rootDocumentListenerHistogram.count(static_cast<TouchTargetAndDispatchResultType>(result));
+}
+
+} // namespace
+
 TouchEvent::TouchEvent()
 {
 }
@@ -46,7 +158,11 @@ TouchEvent::TouchEvent(TouchList* touches, TouchList* targetTouches,
     double platformTimeStamp)
     // Pass a sourceCapabilities including the ability to fire touchevents when creating this touchevent, which is always created from input device capabilities from EventHandler.
     : UIEventWithKeyState(type, true, cancelable, view, 0, modifiers, platformTimeStamp, InputDeviceCapabilities::firesTouchEventsSourceCapabilities()),
-    m_touches(touches), m_targetTouches(targetTouches), m_changedTouches(changedTouches), m_causesScrollingIfUncanceled(causesScrollingIfUncanceled)
+    m_touches(touches),
+    m_targetTouches(targetTouches),
+    m_changedTouches(changedTouches),
+    m_causesScrollingIfUncanceled(causesScrollingIfUncanceled),
+    m_defaultPreventedBeforeCurrentTarget(false)
 {
 }
 
@@ -109,6 +225,15 @@ void TouchEvent::preventDefault()
     }
 }
 
+void TouchEvent::doneDispatchingEventAtCurrentTarget()
+{
+    if (!cancelable())

[Rick Byers, 2016/05/18 18:37:18]

This histogram is going to be swamped out by the (canceled) touchmove events
that occur during a drag, right?  Don't you really want to focus on the events
that can block scrolling - i.e. touchstart and touchmove events that occur
before "movedBeyondSlopRegion" is true?

[tdresser, 2016/05/18 18:57:12]

+1, thanks.

[dtapuska, 2016/05/19 16:11:21]

Done.

+        return;
+    bool canceled = defaultPrevented();
+    logTouchTargetHistogram(currentTarget(), eventPhase(), m_defaultPreventedBeforeCurrentTarget, canceled);
+    m_defaultPreventedBeforeCurrentTarget = canceled;
+}
+
 EventDispatchMediator* TouchEvent::createMediator()
 {
     return TouchEventDispatchMediator::create(this);