Rewire Android WebView's compositor changed signal.

android_webview/BUILD.gn

 # Copyright 2015 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/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/config/locales.gni")
 import("//tools/grit/repack.gni")
 import("system_webview_apk_tmpl.gni")
 import("webview_repack_locales.gni")
@@ skipping 425 matching lines @@
     "browser/aw_result_codes.h",
     "browser/aw_ssl_host_state_delegate.cc",
     "browser/aw_ssl_host_state_delegate.h",
     "browser/aw_web_preferences_populater.cc",
     "browser/aw_web_preferences_populater.h",
     "browser/browser_view_renderer.cc",
     "browser/browser_view_renderer.h",
     "browser/browser_view_renderer_client.h",
     "browser/child_frame.cc",
     "browser/child_frame.h",
+    "browser/compositor_id.cc",
+    "browser/compositor_id.h",
     "browser/deferred_gpu_command_service.cc",
     "browser/deferred_gpu_command_service.h",
     "browser/find_helper.cc",
     "browser/find_helper.h",
     "browser/gl_view_renderer_manager.cc",
     "browser/gl_view_renderer_manager.h",
     "browser/hardware_renderer.cc",
     "browser/hardware_renderer.h",
     "browser/icon_helper.cc",
     "browser/icon_helper.h",
@@ skipping 290 matching lines @@
     android_manifest = get_target_outputs(":system_webview_manifest")
     android_manifest = android_manifest[1]
     android_manifest_dep = ":system_webview_manifest"
     deps = [
       ":system_webview_resources",
       "//android_webview/glue",
     ]
     apk_name = "SystemWebView"
   }
 }