Deal gracefully with null {GraphicsContext,SkPictureBuilder}.endRecording() results.

third_party/WebKit/Source/web/PageWidgetDelegate.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 75 matching lines @@
         FrameView* view = root.view();
         if (view) {
             ClipRecorder clipRecorder(paintContext, root, DisplayItem::PageWidgetDelegateClip, LayoutRect(dirtyRect));
 
             view->paint(paintContext, globalPaintFlags, CullRect(dirtyRect));
         } else if (!DrawingRecorder::useCachedDrawingIfPossible(paintContext, root, DisplayItem::PageWidgetDelegateBackgroundFallback)) {
             DrawingRecorder drawingRecorder(paintContext, root, DisplayItem::PageWidgetDelegateBackgroundFallback, dirtyRect);
             paintContext.fillRect(dirtyRect, Color::white);
         }
     }
-    pictureBuilder.endRecording()->playback(canvas);
+    RefPtr<const SkPicture> recording = pictureBuilder.endRecording();
+    if (recording)
+        recording->playback(canvas);
 }
 
 void PageWidgetDelegate::paint(Page& page, WebCanvas* canvas,
     const WebRect& rect, LocalFrame& root)
 {
     paintInternal(page, canvas, rect, root, GlobalPaintNormalPhase);
 }
 
 void PageWidgetDelegate::paintIgnoringCompositing(Page& page, WebCanvas* canvas,
     const WebRect& rect, LocalFrame& root)
@@ skipping 146 matching lines @@
         WEBINPUT_EVENT_CASE(TouchMove)
         WEBINPUT_EVENT_CASE(TouchEnd)
         WEBINPUT_EVENT_CASE(TouchCancel)
     default:
         ASSERT_NOT_REACHED();
         return "";
     }
 }
 
 } // namespace blink