Convert SetContentSettingRules to use mojo, part 1/2.

components/content_settings/core/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("//mojo/public/tools/bindings/mojom.gni")
+
 static_library("common") {
   sources = [
     "content_settings.cc",
     "content_settings.h",
     "content_settings_pattern.cc",
     "content_settings_pattern.h",
     "content_settings_pattern_parser.cc",
     "content_settings_pattern_parser.h",
     "content_settings_types.h",
     "pref_names.cc",
@@ skipping 17 matching lines @@
   ]
 
   deps = [
     ":common",
     "//net",
     "//testing/gmock",
     "//testing/gtest",
     "//url",
   ]
 }
+
+mojom("mojo_bindings") {
+  sources = [
+    "content_settings.mojom",
+  ]
+}