Add UseCounter for requestPointerLock() usage in Shadow tree.

third_party/WebKit/Source/core/page/PointerLockController.cpp

Index: third_party/WebKit/Source/core/page/PointerLockController.cpp
diff --git a/third_party/WebKit/Source/core/page/PointerLockController.cpp b/third_party/WebKit/Source/core/page/PointerLockController.cpp
index 72ee211b26cb4822e86bb9dcc944cb7bd0592bc0..eeeeea87c1e0c80ba555c6be783bc5009c0dccb3 100644
--- a/third_party/WebKit/Source/core/page/PointerLockController.cpp
+++ b/third_party/WebKit/Source/core/page/PointerLockController.cpp
@@ -53,6 +53,8 @@ void PointerLockController::requestPointerLock(Element* target)
     }
 
     UseCounter::countCrossOriginIframe(target->document(), UseCounter::ElementRequestPointerLockIframe);
+    if (target->isInShadowTree())
+        UseCounter::count(target->document(), UseCounter::ElementRequestPointerLockInShadow);
 
     if (target->document().isSandboxed(SandboxPointerLock)) {
         // FIXME: This message should be moved off the console once a solution to https://bugs.webkit.org/show_bug.cgi?id=103274 exists.