Revert of Drop unecessary use of CrossThreadPersistent by CanvasAsyncBlobCreator.

third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/html/canvas/CanvasAsyncBlobCreator.h"
 
 #include "core/fileapi/Blob.h"
 #include "platform/ThreadSafeFunctional.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "platform/image-encoders/JPEGImageEncoder.h"
@@ skipping 238 matching lines @@
     }
 
     this->signalAlternativeCodePathFinishedForTesting();
 }
 
 void CanvasAsyncBlobCreator::createBlobAndInvokeCallback()
 {
     ASSERT(isMainThread());
     Blob* resultBlob = Blob::create(m_encodedImage->data(), m_encodedImage->size(), convertMimeTypeEnumToString(m_mimeType));
     Platform::current()->mainThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, bind(&BlobCallback::handleEvent, m_callback, resultBlob));
+    // Since toBlob is done, timeout events are no longer needed. So we clear
+    // non-GC members to allow teardown of CanvasAsyncBlobCreator.
+    m_data.clear();
+    m_callback.clear();
 }
 
 void CanvasAsyncBlobCreator::createNullAndInvokeCallback()
 {
     ASSERT(isMainThread());
     Platform::current()->mainThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, bind(&BlobCallback::handleEvent, m_callback, nullptr));
+    // Since toBlob is done (failed), timeout events are no longer needed. So we
+    // clear non-GC members to allow teardown of CanvasAsyncBlobCreator.
+    m_data.clear();
+    m_callback.clear();
 }
 
 void CanvasAsyncBlobCreator::encodeImageOnEncoderThread(double quality)
 {
     ASSERT(!isMainThread());
     ASSERT(m_mimeType == MimeTypeWebp);
 
     if (!ImageDataBuffer(m_size, m_data->data()).encodeImage("image/webp", quality, m_encodedImage.get())) {
         Platform::current()->mainThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, threadSafeBind(&BlobCallback::handleEvent, wrapCrossThreadPersistent(m_callback.get()), nullptr));
         return;
@@ skipping 78 matching lines @@
     }
 }
 
 void CanvasAsyncBlobCreator::postDelayedTaskToMainThread(const WebTraceLocation& location, std::unique_ptr<SameThreadClosure> task, double delayMs)
 {
     DCHECK(isMainThread());
     Platform::current()->mainThread()->getWebTaskRunner()->postDelayedTask(location, std::move(task), delayMs);
 }
 
 } // namespace blink