Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/common/proto/blob_channel.proto

 // 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-package cc.proto;
+package blimp;
 
-message Vector2d {
-  optional int64 x = 1;
-  optional int64 y = 2;
+message TransferBlob {
+  optional string blob_id = 2;

[Wez, 2016/05/24 01:18:40]

nit: You don't think blob_id is likely to be common w/ other messages?

[Kevin M, 2016/05/25 00:06:33]

I was thinking I could make promote it provided that it makes sense for the use
case. For get, we might want to specify multiple IDs at once. Cache digest
upload would use multiple IDs or some kind of efficiently packed digest/Bloom
filter.

[Wez, 2016/05/25 02:47:44]

Acknowledged.

+  optional bytes payload = 1;
 }
+
+message BlobChannelMessage {
+  oneof type {
+    // Engine => Client types.
+    TransferBlob transfer_blob = 1;
+  }
+}