Incorporate BlobChannel into Blimp image encode/decode pipeline.

blimp/engine/mojo/blob_channel.mojom

 // 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 blimp.engine.mojom;
 
 interface BlobChannel {
   // Stores the blob |id| in the BlobCache.
-  Put(string id, array<uint8> data);
+  // TODO(kmarshall): Use shared memory for more efficient data transfer, see
+  // crbug.com/614564 .
+  PutBlob(string id, string data);
 
   // Requests that the BlobChannel push the blob |id| over the wire.
   // The request will be ignored if the BlobChannel knows that
   // the client already has the data.
-  Push(string id);
+  DeliverBlob(string id);
 };