Convert SetContentSettingRules to use mojo, part 1/2.

components/content_settings/core/common/BUILD.gn

Index: components/content_settings/core/common/BUILD.gn
diff --git a/components/content_settings/core/common/BUILD.gn b/components/content_settings/core/common/BUILD.gn
index a73d49ed145f80edd5c17624e114e3cff61bbbe3..617106d206154c50665c0d241013f8acc7924205 100644
--- a/components/content_settings/core/common/BUILD.gn
+++ b/components/content_settings/core/common/BUILD.gn
@@ -2,6 +2,8 @@
 # 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",
@@ -39,3 +41,9 @@ source_set("unit_tests") {
     "//url",
   ]
 }
+
+mojom("mojo_bindings") {
+  sources = [
+    "content_settings.mojom",
+  ]
+}