Fix crash in canvas.toBlob caused by allocation failure

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 4246 matching lines @@
     // TODO(crbug.com/622958): Implement GPU-to-GPU path for WebGL 2 and more internal formats.
     if (functionID == TexSubImage2D && (isWebGL2OrHigher() || extensionEnabled(OESTextureFloatName) || extensionEnabled(OESTextureHalfFloatName) || extensionEnabled(EXTsRGBName)))
         return false;
     return true;
 }
 
 void WebGLRenderingContextBase::texImageCanvasByGPU(HTMLCanvasElement* canvas, GLuint targetTexture, GLenum targetInternalformat, GLenum targetType, GLint targetLevel)
 {
     if (!canvas->is3D()) {
         ImageBuffer* buffer = canvas->buffer();
-        if (!buffer->copyToPlatformTexture(contextGL(), targetTexture, targetInternalformat, targetType,
+        if (buffer && !buffer->copyToPlatformTexture(contextGL(), targetTexture, targetInternalformat, targetType,
             targetLevel, m_unpackPremultiplyAlpha, m_unpackFlipY)) {
             NOTREACHED();
         }
     } else {
         WebGLRenderingContextBase* gl = toWebGLRenderingContextBase(canvas->renderingContext());
         ScopedTexture2DRestorer restorer(gl);
         if (!gl->drawingBuffer()->copyToPlatformTexture(contextGL(), targetTexture, targetInternalformat, targetType,
             targetLevel, m_unpackPremultiplyAlpha, !m_unpackFlipY, BackBuffer)) {
             NOTREACHED();
         }
@@ skipping 2176 matching lines @@
 
 void WebGLRenderingContextBase::getHTMLOrOffscreenCanvas(HTMLCanvasElementOrOffscreenCanvas& result) const
 {
     if (canvas())
         result.setHTMLCanvasElement(canvas());
     else
         result.setOffscreenCanvas(getOffscreenCanvas());
 }
 
 } // namespace blink