Fix race conditions in ImageDecoder.

chrome/browser/media_galleries/fileapi/supported_image_type_validator.cc

 // Copyright 2013 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 "chrome/browser/media_galleries/fileapi/supported_image_type_validator.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file.h"
 #include "base/location.h"
@@ skipping 34 matching lines @@
   }
 
   return result.Pass();
 }
 
 class ImageDecoderDelegateAdapter : public ImageDecoder::ImageRequest {
  public:
   ImageDecoderDelegateAdapter(
       scoped_ptr<std::string> data,
       const storage::CopyOrMoveFileValidator::ResultCallback& callback)
-      : ImageRequest(content::BrowserThread::GetMessageLoopProxyForThread(
-            BrowserThread::IO)),

[Theresa, 2015/04/20 22:35:26]

I'm not familiar enough with this class to know whether or not it's constructed
on the IO thread... or whether or not OnImageDecoded/OnDecodeImageFailed
actually need to be called on the IO thread since they just invoke
CopyOrMoveFileValidator::ResultCallback.Run()?

[Lei Zhang, 2015/04/21 00:44:00]

The only place that calls the ImageDecoderDelegateAdapter ctor is in
SupportedImageTypeValidator::OnFileOpen(), which clearly runs on the IO thread.

-        data_(data.Pass()),
+      : data_(data.Pass()),
         callback_(callback) {
     DCHECK(data_);
   }
 
   const std::string& data() {
     return *data_;
   }
 
   // ImageDecoder::ImageRequest methods.
   void OnImageDecoded(const SkBitmap& /*decoded_image*/) override {
@@ skipping 56 matching lines @@
   if (!data.get()) {
     callback_.Run(base::File::FILE_ERROR_SECURITY);
     return;
   }
 
   // |adapter| will delete itself after a completion message is received.
   ImageDecoderDelegateAdapter* adapter =
       new ImageDecoderDelegateAdapter(data.Pass(), callback_);
   ImageDecoder::Start(adapter, adapter->data());
 }