Measure requestFullscreen() replacing the pending element

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

Index: third_party/WebKit/Source/core/dom/Fullscreen.cpp
diff --git a/third_party/WebKit/Source/core/dom/Fullscreen.cpp b/third_party/WebKit/Source/core/dom/Fullscreen.cpp
index 4868177420a08a5d70d8a964a82150cbe40d5b72..7d3ee2056cb1247c5be7ab1cd725bc0787e2b8f0 100644
--- a/third_party/WebKit/Source/core/dom/Fullscreen.cpp
+++ b/third_party/WebKit/Source/core/dom/Fullscreen.cpp
@@ -481,6 +481,10 @@ void Fullscreen::requestFullscreen(Element& element,
 
     // 5. Return, and run the remaining steps asynchronously.
     // 6. Optionally, perform some animation.
+    if (from(document).m_pendingFullscreenElement) {
+      UseCounter::count(document,
+                        UseCounter::FullscreenRequestWithPendingElement);
+    }
     from(document).m_pendingFullscreenElement = &element;
     document.frame()->chromeClient().enterFullscreen(*document.frame());