Decouple MediaSession messages from WebContents (full patch)

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 = [
@@ skipping 118 matching lines @@
     "interstitial_page_delegate.cc",
     "interstitial_page_delegate.h",
     "invalidate_type.h",
     "javascript_dialog_manager.cc",
     "javascript_dialog_manager.h",
     "load_notification_details.h",
     "local_storage_usage_info.h",
     "media_capture_devices.h",
     "media_device_id.cc",
     "media_device_id.h",
+    "media_session.h",
+    "media_session_observer.cc",
+    "media_session_observer.h",
     "memory_coordinator_delegate.h",
     "memory_pressure_controller.cc",
     "memory_pressure_controller.h",
     "message_port_delegate.h",
     "message_port_provider.h",
     "native_web_keyboard_event.h",
     "navigation_controller.cc",
     "navigation_controller.h",
     "navigation_data.h",
     "navigation_details.cc",
@@ skipping 172 matching lines @@
 
   if (is_android) {
     deps += [ "//ui/android" ]
   }
 
   if (use_aura) {
     sources -= [ "context_factory.h" ]
     deps += [ "//ui/aura" ]
   }
 }