Avoid calling a virtual method on a null document in lifecycle().

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 1348 matching lines @@
     float pageScaleAtLayoutWidth =
         m_frame->host()->visualViewport().size().width() / size.width();
     size.expand(0, browserControls.height() / pageScaleAtLayoutWidth);
   }
 
   size.scale(1 / zoom);
   return size;
 }
 
 DocumentLifecycle& FrameView::lifecycle() const {
+  DCHECK(m_frame);
+  DCHECK(m_frame->document());
   return m_frame->document()->lifecycle();
 }
 
 LayoutReplaced* FrameView::embeddedReplacedContent() const {
   LayoutViewItem layoutViewItem = this->layoutViewItem();
   if (layoutViewItem.isNull())
     return nullptr;
 
   LayoutObject* firstChild = layoutView()->firstChild();
   if (!firstChild || !firstChild->isBox())
@@ skipping 3213 matching lines @@
         else if (frameRect().maxX() < 0)
           frame().document()->maybeRecordLoadReason(WouldLoadLeft);
         else if (!m_hiddenForThrottling)
           frame().document()->maybeRecordLoadReason(WouldLoadVisible);
       }
     }
   }
 }
 
 bool FrameView::shouldThrottleRendering() const {
-  return canThrottleRendering() && lifecycle().throttlingAllowed();
+  return canThrottleRendering() && m_frame->document() &&
+         lifecycle().throttlingAllowed();
 }
 
 bool FrameView::canThrottleRendering() const {
   if (m_lifecycleUpdatesThrottled)
     return true;
   if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
     return false;
   if (m_subtreeThrottled)
     return true;
   // We only throttle hidden cross-origin frames. This is to avoid a situation
@@ skipping 31 matching lines @@
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.width();
 }
 
 int FrameView::initialViewportHeight() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.height();
 }
 
 }  // namespace blink