Add ability to count mouseup/down on disabled form controls.

This will count the number of pages we encounter with mouseup/down
listeners in the event path on disable form controls.

BUG=696686

Change-Id: I73102564444348c150714a8189bcab8738c9fa15
Reviewed-on: https://chromium-review.googlesource.com/847424Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526807}

third_party/WebKit/Source/core/dom/Node.cpp

@@ -2226,8 +2226,16 @@ void Node::HandleLocalEvents(Event& event) {
 
   if (IsDisabledFormControl(this) && event.IsMouseEvent() &&
       !RuntimeEnabledFeatures::SendMouseEventsDisabledFormControlsEnabled()) {
-    UseCounter::Count(GetDocument(),
-                      WebFeature::kDispatchMouseEventOnDisabledFormControl);
+    if (HasEventListeners(event.type())) {
+      UseCounter::Count(GetDocument(),
+                        WebFeature::kDispatchMouseEventOnDisabledFormControl);
+      if (event.type() == EventTypeNames::mousedown ||
+          event.type() == EventTypeNames::mouseup) {
+        UseCounter::Count(
+            GetDocument(),
+            WebFeature::kDispatchMouseUpDownEventOnDisabledFormControl);
+      }
+    }
     return;
   }
 

third_party/WebKit/Source/core/dom/events/EventPath.cpp

@@ -380,6 +380,15 @@ bool EventPath::DisabledFormControlExistsInPath() const {
   return false;
 }
 
+bool EventPath::HasEventListenersInPath(const AtomicString& event_type) const {
+  for (const auto& context : node_event_contexts_) {
+    const Node* target_node = context.GetNode();
+    if (target_node && target_node->HasEventListeners(event_type))
+      return true;
+  }
+  return false;
+}
+
 NodeEventContext& EventPath::TopNodeEventContext() {
   DCHECK(!IsEmpty());
   return Last();

third_party/WebKit/Source/core/dom/events/EventPath.h

@@ -80,6 +80,7 @@ class CORE_EXPORT EventPath final
   void AdjustForTouchEvent(const TouchEvent&);
 
   bool DisabledFormControlExistsInPath() const;
+  bool HasEventListenersInPath(const AtomicString& event_type) const;
 
   NodeEventContext& TopNodeEventContext();
 

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

@@ -27,6 +27,7 @@
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/LocalFrameView.h"
+#include "core/frame/UseCounter.h"
 #include "core/input/InputDeviceCapabilities.h"
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutView.h"
@@ -447,8 +448,19 @@ DispatchEventResult MouseEvent::DispatchEvent(EventDispatcher& dispatcher) {
     return dispatcher.Dispatch();
 
   if (!send_to_disabled_form_controls &&
-      IsDisabledFormControl(&dispatcher.GetNode()))
+      IsDisabledFormControl(&dispatcher.GetNode())) {
+    if (GetEventPath().HasEventListenersInPath(type())) {
+      UseCounter::Count(dispatcher.GetNode().GetDocument(),
+                        WebFeature::kDispatchMouseEventOnDisabledFormControl);
+      if (type() == EventTypeNames::mousedown ||
+          type() == EventTypeNames::mouseup) {
+        UseCounter::Count(
+            dispatcher.GetNode().GetDocument(),
+            WebFeature::kDispatchMouseUpDownEventOnDisabledFormControl);
+      }
+    }
     return DispatchEventResult::kCanceledBeforeDispatch;
+  }
 
   if (type().IsEmpty())
     return DispatchEventResult::kNotCanceled;  // Shouldn't happen.

third_party/WebKit/public/platform/web_feature.mojom

@@ -1827,6 +1827,7 @@ enum WebFeature {
   kCSSSelectorWebkitTextfieldDecorationContainer = 2318,
   kCSSSelectorWebkitUnknownPseudo = 2319,
   kFilterAsContainingBlockMayChangeOutput = 2320,
+  kDispatchMouseUpDownEventOnDisabledFormControl = 2321,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

tools/metrics/histograms/enums.xml

@@ -17333,6 +17333,7 @@ Called by update_net_error_codes.py.-->
   <int value="2318" label="CSSSelectorWebkitTextfieldDecorationContainer"/>
   <int value="2319" label="CSSSelectorWebkitUnknownPseudo"/>
   <int value="2320" label="FilterAsContainingBlockMayChangeOutput"/>
+  <int value="2321" label="DispatchMouseUpDownEventOnDisabledFormControl"/>
 </enum>
 
 <enum name="FeedbackSource">