Add use count for click retargeting due to capture

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/input/MouseEventManager.h"
 
 #include "core/clipboard/DataObject.h"
 #include "core/clipboard/DataTransfer.h"
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
@@ skipping 215 matching lines @@
 
   setNodeUnderMouse(targetNode, canvasRegionId, webMouseEvent);
 
   return dispatchMouseEvent(m_nodeUnderMouse, eventType, webMouseEvent,
                             canvasRegionId, nullptr);
 }
 
 WebInputEventResult MouseEventManager::dispatchMouseClickIfNeeded(
     Node* target,
     const WebMouseEvent& mouseEvent,
-    const String& canvasRegionId) {
+    const String& canvasRegionId,
+    Node* targetWithoutCapture) {
   // We only prevent click event when the click may cause contextmenu to popup.
   // However, we always send auxclick.
   bool contextMenuEvent =
       !RuntimeEnabledFeatures::auxclickEnabled() &&
       mouseEvent.button == WebPointerProperties::Button::Right;
 #if OS(MACOSX)
   // FIXME: The Mac port achieves the same behavior by checking whether the
   // context menu is currently open in WebPage::mouseEvent(). Consider merging
   // the implementations.
   if (mouseEvent.button == WebPointerProperties::Button::Left &&
@@ skipping 13 matching lines @@
     // Unless distribution is updated, commonAncestor would hit ASSERT.
     if (m_clickNode == target) {
       clickTargetNode = m_clickNode;
       clickTargetNode->updateDistribution();
     } else if (m_clickNode->document() == target->document()) {
       m_clickNode->updateDistribution();
       target->updateDistribution();
       clickTargetNode = target->commonAncestor(
           *m_clickNode, EventHandlingUtil::parentForClickEvent);
     }
+
+    // This block is only for the purpose of gathering the metric and can be
+    // removed as soon as we don't need the metric.
+    if (targetWithoutCapture != target) {
+      Node* alternativeClickTargetNode = nullptr;
+      if (m_clickNode == targetWithoutCapture) {
+        alternativeClickTargetNode = m_clickNode;
+      } else if (m_clickNode->document() == targetWithoutCapture->document()) {
+        alternativeClickTargetNode = targetWithoutCapture->commonAncestor(
+            *m_clickNode, EventHandlingUtil::parentForClickEvent);
+      }
+      if (alternativeClickTargetNode != clickTargetNode) {
+        UseCounter::count(m_frame,
+                          UseCounter::PointerEventClickRetargetCausedByCapture);
+      }
+    }
+
     if (clickTargetNode) {
       clickEventResult = dispatchMouseEvent(
           clickTargetNode,
           !RuntimeEnabledFeatures::auxclickEnabled() ||
                   (mouseEvent.button == WebPointerProperties::Button::Left)
               ? EventTypeNames::click
               : EventTypeNames::auxclick,
           mouseEvent, canvasRegionId, nullptr);
     }
   }
@@ skipping 739 matching lines @@
 
 void MouseEventManager::setClickCount(int clickCount) {
   m_clickCount = clickCount;
 }
 
 bool MouseEventManager::mouseDownMayStartDrag() {
   return m_mouseDownMayStartDrag;
 }
 
 }  // namespace blink