Convert 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 5f3dbaa9e04ced04edbc90594fdf40c68b7a482e..9c0fa77d6ea9c72f9f33c4eddfdb411961c1cddb 100644
--- a/chrome/browser/image_decoder.h
+++ b/chrome/browser/image_decoder.h
@@ -12,6 +12,7 @@
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
 #include "base/synchronization/lock.h"
@@ -22,6 +23,14 @@
 
 class SkBitmap;
 
+namespace mojom {
+class ImageDecoder;
+}
+
+namespace mojo {
+template <typename T> class InterfacePtr;
+}
+
 // This is a helper class for decoding images safely in a utility process. To
 // use this, call ImageDecoder::Start(...) or
 // ImageDecoder::StartWithOptions(...) on any thread.
@@ -155,6 +164,10 @@ class ImageDecoder : public content::UtilityProcessHostClient {
   // unless a new decoding request resets the timer.
   scoped_ptr<base::DelayTimer> batch_mode_timer_;
 
+  // Mojo service connection. Must always be bound/reset and used on the IO
+  // thread.
+  scoped_ptr<mojo::InterfacePtr<mojom::ImageDecoder>> decoder_;

[jam, 2016/03/31 17:46:33]

why is this in a scoped ptr instead of having the raw interfaceptr as we usually
do? 

[Anand Mistry (off Chromium), 2016/04/01 05:35:11]

Oops. Artifact of the previous (in components) incarnation where I wanted to
avoid exposing mojo. Not necessary any more.

+
   DISALLOW_COPY_AND_ASSIGN(ImageDecoder);
 };