[OnionSoup] Move background_sync.mojom from //content to //third_party/WebKit

content/public/common/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/buildflag_header.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/features.gni")
 import("//content/common/common.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//third_party/webrtc/build/webrtc.gni")
@@ skipping 120 matching lines @@
   }
 
   if (enable_webrtc) {
     sources += [
       "webrtc_ip_handling_policy.cc",
       "webrtc_ip_handling_policy.h",
     ]
   }
 }
 
-mojom("mojo_bindings") {
-  sources = [
-    "background_sync.mojom",
-    "service_worker_event_status.mojom",
-  ]
-}
-
 buildflag_header("features") {
   header = "features.h"
 
   flags = [ "RTC_USE_H264=$rtc_use_h264" ]
 }
 
 source_set("feature_h264_with_openh264_ffmpeg") {
   deps = [
     ":features",
     "//base",
   ]
   sources = [
     "feature_h264_with_openh264_ffmpeg.cc",
     "feature_h264_with_openh264_ffmpeg.h",
   ]
 }