scheduler: Throttle timers in out-of-view frames

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 4117 matching lines @@
     m_needsUpdateViewportIntersectionInSubtree = false;
 
     for (Frame* child = m_frame->tree().firstChild(); child; child = child->tree().nextSibling()) {
         if (!child->isLocalFrame())
             continue;
         if (FrameView* view = toLocalFrame(child)->view())
             view->updateViewportIntersectionsForSubtree(phases);
     }
 }
 
 void FrameView::updateThrottlingStatus()

[alex clarke (OOO till 29th), 2016/06/28 17:11:28]

Does this get called often?

[Sami, 2016/06/28 17:22:45]

Only when a frame enters or leaves the viewport. Movement fully inside or
outside the viewport doesn't trigger this work.

 {
     // Only offscreen frames can be throttled.
     m_hiddenForThrottling = m_viewportIntersectionValid && m_viewportIntersection.isEmpty();
+    m_frame->frameScheduler()->setFrameVisible(!m_hiddenForThrottling);
 
     // We only throttle the rendering pipeline in cross-origin frames. This is
     // to avoid a situation where an ancestor frame directly depends on the
     // pipeline timing of a descendant and breaks as a result of throttling.
     // The rationale is that cross-origin frames must already communicate with
     // asynchronous messages, so they should be able to tolerate some delay in
     // receiving replies from a throttled peer.
     //
     // Check if we can access our parent's security origin.
     m_crossOriginForThrottling = false;
     // If any of our parents are throttled, we must be too.
     m_subtreeThrottled = false;
     const SecurityOrigin* origin = frame().securityContext()->getSecurityOrigin();
     for (Frame* parentFrame = m_frame->tree().parent(); parentFrame; parentFrame = parentFrame->tree().parent()) {
         const SecurityOrigin* parentOrigin = parentFrame->securityContext()->getSecurityOrigin();
         if (!origin->canAccess(parentOrigin))
             m_crossOriginForThrottling = true;
         if (parentFrame->isLocalFrame() && toLocalFrame(parentFrame)->view() && toLocalFrame(parentFrame)->view()->canThrottleRendering())
             m_subtreeThrottled = true;
     }
+    m_frame->frameScheduler()->setCrossOrigin(m_crossOriginForThrottling);
 }
 
 void FrameView::notifyRenderThrottlingObserversForTesting()
 {
     DCHECK(m_renderThrottlingObserverNotificationFactory->isPending());
     notifyRenderThrottlingObservers();
 }
 
 void FrameView::notifyRenderThrottlingObservers()
 {
@@ skipping 58 matching lines @@
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 LayoutBox& FrameView::boxForScrollControlPaintInvalidation() const
 {
     ASSERT(!layoutViewItem().isNull());
     return *layoutView();
 }
 
 } // namespace blink