Convert the utility process image decoder into a Mojo service.

chrome/common/image_decoder.mojom

Index: chrome/common/image_decoder.mojom
diff --git a/chrome/common/image_decoder.mojom b/chrome/common/image_decoder.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..3467afa4e06bf59e50f547b4f68056e52ebab1ac
--- /dev/null
+++ b/chrome/common/image_decoder.mojom
@@ -0,0 +1,18 @@
+// Copyright 2016 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.
+
+module mojom;
+
+import "skia/public/interfaces/bitmap.mojom";
+
+enum ImageCodec {
+  DEFAULT,
+  ROBUST_JPEG,
+  ROBUST_PNG,
+};
+
+interface ImageDecoder {
+  DecodeImage(array<uint8> encoded_data, ImageCodec codec, bool shrink_to_fit)
+      => (skia.mojom.Bitmap? decoded_image);
+};