Add use count for click retargeting due to capture

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

Index: third_party/WebKit/Source/core/input/MouseEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/MouseEventManager.cpp b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
index 3672b0fa43f8f76190a6cdaffc828cdb4de6aa81..8649084de97f92988e9453a00c88478142c24961 100644
--- a/third_party/WebKit/Source/core/input/MouseEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
@@ -233,7 +233,8 @@ WebInputEventResult MouseEventManager::setMousePositionAndDispatchMouseEvent(
 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 =
@@ -267,6 +268,23 @@ WebInputEventResult MouseEventManager::dispatchMouseClickIfNeeded(
       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,