ChannelMojo: Replace hand written messsages with mojo.

ipc/mojo/BUILD.gn

Index: ipc/mojo/BUILD.gn
diff --git a/ipc/mojo/BUILD.gn b/ipc/mojo/BUILD.gn
index 29905bdb664848f6b0f736ae585aee994c78b3a6..324cc9ac9aa85e7817644f1d60cafbdb6585cd2f 100644
--- a/ipc/mojo/BUILD.gn
+++ b/ipc/mojo/BUILD.gn
@@ -2,8 +2,17 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//mojo/public/tools/bindings/mojom.gni")
+
+mojom("client_channel") {
+  sources = [
+    "client_channel.mojom",
+  ]
+}
+
 component("mojo") {
   sources = [
+    "client_channel.mojom",
     "ipc_channel_mojo.cc",
     "ipc_channel_mojo.h",
     "ipc_channel_mojo_host.cc",
@@ -25,6 +34,7 @@ component("mojo") {
     "//mojo/environment:chromium",
     "//mojo/public/cpp/bindings",
     "//mojo/edk/system",
+    ":client_channel",
   ]
 }