Log to UMA when x-origin frames (1) are created and (2) become visible

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 4252 matching lines @@
 void FrameView::notifyRenderThrottlingObserversForTesting()
 {
     DCHECK(m_renderThrottlingObserverNotificationFactory->isPending());
     notifyRenderThrottlingObservers();
 }
 
 void FrameView::notifyRenderThrottlingObservers()
 {
     TRACE_EVENT0("blink", "FrameView::notifyRenderThrottlingObservers");
     DCHECK(!isInPerformLayout());
-    DCHECK(!m_frame->document() || !m_frame->document()->inStyleRecalc());
+    DCHECK(frame().document());
+    DCHECK(!frame().document()->inStyleRecalc());
     bool wasThrottled = canThrottleRendering();
 
     updateThrottlingStatus();
 
+    frame().document()->onVisibilityMaybeChanged(!m_hiddenForThrottling);
+
     bool becameThrottled = !wasThrottled && canThrottleRendering();
     bool becameUnthrottled = wasThrottled && !canThrottleRendering();
     ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator();
     if (becameThrottled) {
         // If this FrameView became throttled, we must make sure all of its
         // children become throttled at the same time. Otherwise we might
         // attempt to paint one of the children with an out-of-date layout
         // before |notifyRenderThrottlingObservers| has made it throttled.
         forAllNonThrottledFrameViews([](FrameView& frameView) {
             frameView.m_subtreeThrottled = true;
@@ skipping 35 matching lines @@
 }
 
 bool FrameView::canThrottleRendering() const
 {
     if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
         return false;
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 } // namespace blink