Turn the utility process image decoder into a Mojo service.

chrome/browser/image_decoder.h

Index: chrome/browser/image_decoder.h
diff --git a/chrome/browser/image_decoder.h b/chrome/browser/image_decoder.h
index 2206dd9f454ebcbfc3a29674cf41e1d42eb594ee..fa9e7e10eaeafb47f4059a8c66f82e3767bb94f1 100644
--- a/chrome/browser/image_decoder.h
+++ b/chrome/browser/image_decoder.h
@@ -12,11 +12,13 @@
 #include "base/memory/ref_counted.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "content/public/browser/utility_process_host_client.h"
+#include "services/image_decoder/public/interfaces/image_decoder.mojom.h"
 
 class SkBitmap;
 
 // Decodes an image in a sandboxed process.
-class ImageDecoder : public content::UtilityProcessHostClient {
+class ImageDecoder : public content::UtilityProcessHostClient,
+                     public mojo::ErrorHandler {
  public:
   class Delegate {
    public:
@@ -65,6 +67,9 @@ class ImageDecoder : public content::UtilityProcessHostClient {
   // Overidden from UtilityProcessHostClient:
   bool OnMessageReceived(const IPC::Message& message) override;
 
+  // Overidden from mojo::ErrorHandler:
+  void OnConnectionError() override;
+
   // IPC message handlers.
   void OnDecodeImageSucceeded(const SkBitmap& decoded_image);
   void OnDecodeImageFailed();
@@ -72,11 +77,15 @@ class ImageDecoder : public content::UtilityProcessHostClient {
   // Launches sandboxed process that will decode the image.
   void DecodeImageInSandbox(const std::vector<unsigned char>& image_data);
 
+  // Mojo RPC callback.
+  void OnDecodeImageDone(bool success, skia::BitmapPtr image);

[sky, 2015/04/01 15:00:45]

Do we need to distinguish between failure and an empty image? I'm wondering if
we can get away without the success arg. That you only notify
OnDecodeImageSucceeded on success and non-empty image seems to indicate you
don't know the success boolean.

[Anand Mistry (off Chromium), 2015/04/02 04:29:45]

Done.

+
   Delegate* delegate_;
   std::vector<unsigned char> image_data_;
   const ImageCodec image_codec_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
-  bool shrink_to_fit_; // if needed for IPC msg size limit
+  bool shrink_to_fit_;  // if needed for IPC msg size limit
+  services::ImageDecoderPtr decoder_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDecoder);
 };