Mandoline: Move content_handler.mojom from third_party/ to mojo/.

third_party/mojo_services/src/content_handler/public/interfaces/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/module_args/mojo.gni")
-import("$mojo_sdk_root/mojo/public/tools/bindings/mojom.gni")
-
-mojom("interfaces") {
-  sources = [
-    "content_handler.mojom",
-  ]
-
-  import_dirs = [ get_path_info("../../../", "abspath") ]
-
-  if (defined(mojo_network_service_root)) {
-    import_dirs += [ mojo_network_service_root ]
-  } else {
-    mojo_network_service_root = "../../.."
-  }
-
-  deps = [
-    "$mojo_network_service_root/network/public/interfaces",
-    "//mojo/application/public/interfaces",
-  ]
-}