Add UseCounter for setPointerCapture outside dispatch

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

Index: third_party/WebKit/Source/core/input/PointerEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/PointerEventManager.cpp b/third_party/WebKit/Source/core/input/PointerEventManager.cpp
index 5fda74694a4665f5ad226643ee8da6c05fb57af7..429ff1fe33245be210353d475b4108d5f02639c1 100644
--- a/third_party/WebKit/Source/core/input/PointerEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/PointerEventManager.cpp
@@ -66,6 +66,7 @@ void PointerEventManager::clear() {
   m_nodeUnderPointer.clear();
   m_pointerCaptureTarget.clear();
   m_pendingPointerCaptureTarget.clear();
+  m_dispatchingPointerId = 0;
 }
 
 DEFINE_TRACE(PointerEventManager) {
@@ -143,6 +144,7 @@ WebInputEventResult PointerEventManager::dispatchPointerEvent(
 
   // Set whether node under pointer has received pointerover or not.
   const int pointerId = pointerEvent->pointerId();
+
   const AtomicString& eventType = pointerEvent->type();
   if ((eventType == EventTypeNames::pointerout ||
        eventType == EventTypeNames::pointerover) &&
@@ -159,12 +161,15 @@ WebInputEventResult PointerEventManager::dispatchPointerEvent(
   if (!RuntimeEnabledFeatures::pointerEventEnabled())
     return WebInputEventResult::NotHandled;
   if (!checkForListener || target->hasEventListeners(eventType)) {
-    UseCounter::count(m_frame->document(), UseCounter::PointerEventDispatch);
+    UseCounter::count(m_frame, UseCounter::PointerEventDispatch);
     if (eventType == EventTypeNames::pointerdown)
-      UseCounter::count(m_frame->document(),
-                        UseCounter::PointerEventDispatchPointerDown);
+      UseCounter::count(m_frame, UseCounter::PointerEventDispatchPointerDown);
 
+    DCHECK(!m_dispatchingPointerId);
+    m_dispatchingPointerId = pointerId;

[dtapuska, 2017/01/16 21:07:41]

You able to use an AutoReset here?

[Rick Byers, 2017/01/20 22:37:22]

Done.

     DispatchEventResult dispatchResult = target->dispatchEvent(pointerEvent);
+    m_dispatchingPointerId = 0;
+
     return EventHandlingUtil::toWebInputEventResult(dispatchResult);
   }
   return WebInputEventResult::NotHandled;
@@ -623,9 +628,14 @@ void PointerEventManager::elementRemoved(EventTarget* target) {
 
 void PointerEventManager::setPointerCapture(int pointerId,
                                             EventTarget* target) {
-  UseCounter::count(m_frame->document(), UseCounter::PointerEventSetCapture);
-  if (m_pointerEventFactory.isActiveButtonsState(pointerId))
+  UseCounter::count(m_frame, UseCounter::PointerEventSetCapture);
+  if (m_pointerEventFactory.isActiveButtonsState(pointerId)) {
+    if (pointerId != m_dispatchingPointerId) {
+      UseCounter::count(m_frame,
+                        UseCounter::PointerEventSetCaptureOutsideDispatch);

[Navid Zolghadr, 2017/01/16 21:15:01]

There is one more place (as of a "temporary" hack) that we fire pointerevents:

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/Node....

This will mis-count the ones that are coming from the handler of those events.

[Rick Byers, 2017/01/20 22:37:22]

Whoa, that looks potentially bad - commented on the bug.  I don't see an easy
way to handle that weird case, so I think the right answer is just to depend on
the fix for that bug.  In those cases pointer capture is generally going to be
broken anyway because isActiveButtonsState above will return false since
PointerEventManager never saw the pointerdown event.  Even if I did get the
metric hacked into those cases, it'll still be an innacurate measure of the risk
due to setPointerCapture itself failing in some of those cases when it should be
succeeding.

So I suggest we just proceed with this code as-is with the understanding that
the metric may be off until crbug.com/665924 is fixed.  My hunch is that it
won't be off by much (since setPointerCapture is probably rare in
Flash/pointerlock/etc cases) - but I guess we'll find out...

+    }
     m_pendingPointerCaptureTarget.set(pointerId, target);
+  }
 }
 
 void PointerEventManager::releasePointerCapture(int pointerId,