Add missing null pointer check in HTMLCanvasElement.cpp

third_party/WebKit/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 97 matching lines @@
 
 // A default value of quality argument for toDataURL and toBlob
 // It is in an invalid range (outside 0.0 - 1.0) so that it will not be
 // misinterpreted as a user-input value
 const int UndefinedQualityValue = -1.0;
 
 sk_sp<SkImage> createTransparentSkImage(const IntSize& size) {
   DCHECK(ImageBuffer::canCreateImageBuffer(size));
   sk_sp<SkSurface> surface =
       SkSurface::MakeRasterN32Premul(size.width(), size.height());
-  return surface->makeImageSnapshot();
+  return surface ? surface->makeImageSnapshot() : nullptr;
 }
 
 PassRefPtr<Image> createTransparentImage(const IntSize& size) {
   sk_sp<SkImage> image = createTransparentSkImage(size);
   return image ? StaticBitmapImage::create(image) : nullptr;
 }
 
 }  // namespace
 
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
@@ skipping 1284 matching lines @@
   m_surfaceLayerBridge = WTF::wrapUnique(new CanvasSurfaceLayerBridge(this));
   // Creates a placeholder layer first before Surface is created.
   m_surfaceLayerBridge->createSolidColorLayer();
 }
 
 void HTMLCanvasElement::OnWebLayerReplaced() {
   setNeedsCompositingUpdate();
 }
 
 }  // namespace blink