Move MessagePort implementation from android_webview to content

content/public/browser/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/ui.gni")
 
 # See //content/BUILD.gn for how this works.
 group("browser") {
   if (is_component_build) {
     public_deps = [
       "//content",
     ]
   } else {
     public_deps = [
       ":browser_sources",
     ]
   }
 }
 
 source_set("browser_sources") {
   # External code should depend on via ":browser" above.
   visibility = [ "//content/*" ]
 
   sources = [
+    "android/app_web_message_port_service.h",
     "android/browser_media_player_manager_register.cc",
     "android/browser_media_player_manager_register.h",
     "android/compositor.h",
     "android/compositor_client.h",
     "android/content_protocol_handler.h",
     "android/content_view_core.h",
     "android/content_view_layer_renderer.h",
     "android/devtools_auth.h",
     "android/interface_provider_android.h",
     "android/interface_registry_android.h",
@@ skipping 279 matching lines @@
 
   if (is_android) {
     deps += [ "//ui/android" ]
   }
 
   if (use_aura) {
     sources -= [ "context_factory.h" ]
     deps += [ "//ui/aura" ]
   }
 }