Catch utility process StartBatchMode failures

chrome/browser/image_decoder.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_IMAGE_DECODER_H_
 #define CHROME_BROWSER_IMAGE_DECODER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 67 matching lines @@
   static void Cancel(ImageRequest* image_request);
 
  private:
   friend struct base::DefaultLazyInstanceTraits<ImageDecoder>;
 
   ImageDecoder();
   // It's a reference counted object, so destructor is private.
   ~ImageDecoder() override;
 
   // Sends a request to the sandboxed process to decode the image. Starts
-  // batch mode if necessary.
+  // batch mode if necessary. If the utility process fails to start,
+  // an OnDecodeImageFailed task is posted to image_request's |task_runner_|.
   void DecodeImageInSandbox(ImageRequest* image_request,
                             const std::vector<unsigned char>& image_data,
                             ImageCodec image_codec,
                             bool shrink_to_fit);
 
   void CancelImpl(ImageRequest* image_request);
 
   using RequestMap = std::map<int, ImageRequest*>;
 
   // Starts UtilityProcessHost in batch mode and starts |batch_mode_timer_|.
+  // If the utility process fails to start, the method resets
+  // |utility_process_host_| and returns.
   void StartBatchMode();
 
   // Stops batch mode if no requests have come in since
   // kBatchModeTimeoutSeconds.
   void StopBatchMode();
 
   // Overidden from UtilityProcessHostClient.
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // IPC message handlers.
@@ skipping 15 matching lines @@
   // Calls StopBatchMode after kBatchModeTimeoutSeconds have elapsed.
   base::RepeatingTimer<ImageDecoder> batch_mode_timer_;
 
   // The time Start was last called.
   base::TimeTicks last_request_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDecoder);
 };
 
 #endif  // CHROME_BROWSER_IMAGE_DECODER_H_