Make slider thumb painting bail out when the node is null.

Source/core/rendering/RenderMediaControls.cpp

 /*
  * Copyright (C) 2009 Apple Inc.
  * Copyright (C) 2009 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 228 matching lines @@
             paintSliderRangeHighlight(rect, style, context, currentPosition, endPosition, startColor, endColor);
 
         return true;
     }
 
     return true;
 }
 
 static bool paintMediaSliderThumb(RenderObject* object, const PaintInfo& paintInfo, const IntRect& rect)
 {
-    ASSERT(object->node());
+    if (!object->node())
+        return false;
+
     HTMLMediaElement* mediaElement = toParentMediaElement(object->node()->shadowHost());
     if (!mediaElement)
         return false;
 
     if (!hasSource(mediaElement))
         return true;
 
     Image* mediaSliderThumb = getMediaSliderThumb();
     return paintMediaButton(paintInfo.context, rect, mediaSliderThumb);
 }
@@ skipping 32 matching lines @@
     Color startColor = Color(195, 195, 195);
     Color endColor = Color(217, 217, 217);
 
     paintSliderRangeHighlight(rect, style, context, 0.0, fillWidth, startColor, endColor);
 
     return true;
 }
 
 static bool paintMediaVolumeSliderThumb(RenderObject* object, const PaintInfo& paintInfo, const IntRect& rect)
 {
-    ASSERT(object->node());
+    if (!object->node())
+        return false;
+
     HTMLMediaElement* mediaElement = toParentMediaElement(object->node()->shadowHost());
     if (!mediaElement)
         return false;
 
     if (!hasSource(mediaElement) || !mediaElement->hasAudio())
         return true;
 
     static Image* mediaVolumeSliderThumb = platformResource("mediaplayerVolumeSliderThumb");
     return paintMediaButton(paintInfo.context, rect, mediaVolumeSliderThumb);
 }
@@ skipping 121 matching lines @@
 {
     return formatChromiumMediaControlsTime(time, time);
 }
 
 String RenderMediaControls::formatMediaControlsCurrentTime(float currentTime, float duration)
 {
     return formatChromiumMediaControlsTime(currentTime, duration);
 }
 
 } // namespace blink