Adding a null pointer check in HTMLCanvasElement::didRecalcStyle

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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 124 matching lines @@
 LayoutObject* HTMLCanvasElement::createLayoutObject(const ComputedStyle& style)
 {
     LocalFrame* frame = document().frame();
     if (frame && frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return new LayoutHTMLCanvas(this);
     return HTMLElement::createLayoutObject(style);
 }
 
 void HTMLCanvasElement::didRecalcStyle(StyleRecalcChange)
 {
-    SkFilterQuality filterQuality = ensureComputedStyle()->imageRendering() == ImageRenderingPixelated ? kNone_SkFilterQuality : kLow_SkFilterQuality;
+    SkFilterQuality filterQuality;
+    const ComputedStyle* style = ensureComputedStyle();
+    if (style && style->imageRendering() == ImageRenderingPixelated) {
+        filterQuality = kNone_SkFilterQuality;
+    } else {
+        filterQuality = kLow_SkFilterQuality;
+    }
+
     if (is3D()) {
         m_context->setFilterQuality(filterQuality);
         setNeedsCompositingUpdate();
     } else if (hasImageBuffer()) {
         m_imageBuffer->setFilterQuality(filterQuality);
     }
 }
 
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
 {
@@ skipping 736 matching lines @@
 {
     return FloatSize(width(), height());
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // blink