cc/blimp: Add synchronization for scroll/scale state.

cc/proto/client_state_update.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 blimp;
+import "vector2df.proto";
 
-message TransferBlob {
-  optional string blob_id = 1;
-  optional bytes payload = 2;
+package cc.proto;
+
+message ScrollUpdate {
+  optional int32 layer_id = 1;
+  optional Vector2dF scroll_delta = 2;
 }
 
-message BlobChannelMessage {
-  oneof type {
-    // Engine => Client types.
-    TransferBlob transfer_blob = 1;
-  }
-}
+message ClientStateUpdate {
+  repeated ScrollUpdate scroll_updates = 1;
+  optional float page_scale_delta = 2;
+}