Fix build failure with "enable_webrtc = false".

content/public/renderer/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/features.gni")
 
 # See //content/BUILD.gn for how this works.
 group("renderer") {
   if (is_component_build) {
     public_deps = [
@@ skipping 20 matching lines @@
     "android_content_detection_prefixes.h",
     "browser_plugin_delegate.cc",
     "browser_plugin_delegate.h",
     "chrome_object_extensions_utils.cc",
     "chrome_object_extensions_utils.h",
     "content_renderer_client.cc",
     "content_renderer_client.h",
     "context_menu_client.h",
     "document_state.cc",
     "document_state.h",
-    "media_stream_audio_renderer.h",
-    "media_stream_audio_sink.cc",
-    "media_stream_audio_sink.h",
-    "media_stream_sink.h",
-    "media_stream_video_renderer.h",
     "navigation_state.cc",
     "navigation_state.h",
     "pepper_plugin_instance.h",
     "platform_event_observer.h",
     "render_accessibility.h",
     "render_frame.h",
     "render_frame_observer.cc",
     "render_frame_observer.h",
     "render_frame_observer_tracker.h",
     "render_thread.cc",
@@ skipping 33 matching lines @@
   ]
 
   allow_circular_includes_from = [
     # This target is a pair with content/renderer. They always go together and
     # include headers from each other.
     "//content/renderer",
   ]
 
   if (enable_webrtc) {
     sources += [
+      "media_stream_audio_renderer.h",
+      "media_stream_audio_sink.cc",
+      "media_stream_audio_sink.h",
       "media_stream_renderer_factory.h",
+      "media_stream_sink.h",
       "media_stream_utils.cc",
       "media_stream_utils.h",
+      "media_stream_video_renderer.h",
       "media_stream_video_sink.cc",
       "media_stream_video_sink.h",
       "webrtc_log_message_delegate.h",
     ]
     deps += [
       "//content/public/common:feature_h264_with_openh264_ffmpeg",
       "//content/public/common:features",
       "//third_party/webrtc",
     ]
   }
 
   if (enable_plugins) {
     sources += [ "plugin_instance_throttler.h" ]
   }
 }