Make toDataURL robust with respect to allocation failures

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 607 matching lines @@
 {
     ImageData* imageData;
     if (is3D()) {
         // Get non-premultiplied data because of inaccurate premultiplied alpha conversion of buffer()->toDataURL().
         imageData = m_context->paintRenderingResultsToImageData(sourceBuffer);
         if (imageData)
             return imageData;
 
         m_context->paintRenderingResultsToCanvas(sourceBuffer);
         imageData = ImageData::create(m_size);
-        if (hasImageBuffer()) {
+        if (imageData && hasImageBuffer()) {
             sk_sp<SkImage> snapshot = buffer()->newSkImageSnapshot(PreferNoAcceleration, reason);
             if (snapshot) {
                 SkImageInfo imageInfo = SkImageInfo::Make(width(), height(), kRGBA_8888_SkColorType, kUnpremul_SkAlphaType);
                 snapshot->readPixels(imageInfo, imageData->data()->data(), imageInfo.minRowBytes(), 0, 0);
             }
         }
         return imageData;
     }
 
     imageData = ImageData::create(m_size);
 
-    if (!m_context)
+    if (!m_context || !imageData)
         return imageData;
 
     DCHECK(m_context->is2d());
     if (hasImageBuffer()) {
         sk_sp<SkImage> snapshot = buffer()->newSkImageSnapshot(PreferNoAcceleration, reason);
         if (snapshot) {
             SkImageInfo imageInfo = SkImageInfo::Make(width(), height(), kRGBA_8888_SkColorType, kUnpremul_SkAlphaType);
             snapshot->readPixels(imageInfo, imageData->data()->data(), imageInfo.minRowBytes(), 0, 0);
         }
     }
 
     return imageData;
 }
 
 String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double& quality, SourceDrawingBuffer sourceBuffer) const
 {
     if (!isPaintable())
         return String("data:,");
 
     String encodingMimeType = toEncodingMimeType(mimeType, EncodeReasonToDataURL);
 
     ImageData* imageData = toImageData(sourceBuffer, SnapshotReasonToDataURL);
 
+    if (!imageData) // allocation failure
+        return String("data:,");
+
     return ImageDataBuffer(imageData->size(), imageData->data()->data()).toDataURL(encodingMimeType, quality);
 }
 
 String HTMLCanvasElement::toDataURL(const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState) const
 {
     if (surfaceLayerBridge()) {
         exceptionState.throwDOMException(InvalidStateError, "canvas.toDataURL is not allowed for a canvas that has transferred its control to offscreen.");
         return String();
     }
     if (!originClean()) {
@@ skipping 62 matching lines @@
     double quality = UndefinedQualityValue;
     if (!qualityArgument.isEmpty()) {
         v8::Local<v8::Value> v8Value = qualityArgument.v8Value();
         if (v8Value->IsNumber()) {
             quality = v8Value.As<v8::Number>()->Value();
         }
     }
 
     String encodingMimeType = toEncodingMimeType(mimeType, EncodeReasonToBlobCallback);
 
     ImageData* imageData = toImageData(BackBuffer, SnapshotReasonToBlob);

[xlai (Olivia), 2016/09/22 17:51:11]

toBlob is also calling toImageData(). Could you write the failure response in
toBlob as well?

 
     CanvasAsyncBlobCreator* asyncCreator = CanvasAsyncBlobCreator::create(imageData->data(), encodingMimeType, imageData->size(), callback, startTime, document());
 
     bool useIdlePeriodScheduling = (encodingMimeType != "image/webp");
     asyncCreator->scheduleAsyncBlobCreation(useIdlePeriodScheduling, quality);
 }
 
 void HTMLCanvasElement::addListener(CanvasDrawListener* listener)
 {
     m_listeners.add(listener);
@@ skipping 530 matching lines @@
 
 bool HTMLCanvasElement::createSurfaceLayer()
 {
     DCHECK(!m_surfaceLayerBridge);
     std::unique_ptr<CanvasSurfaceLayerBridgeClient> bridgeClient = wrapUnique(new CanvasSurfaceLayerBridgeClientImpl());
     m_surfaceLayerBridge = wrapUnique(new CanvasSurfaceLayerBridge(std::move(bridgeClient)));
     return m_surfaceLayerBridge->createSurfaceLayer(this->width(), this->height());
 }
 
 } // namespace blink