Add module suffix in .mojom files for components/arc

components/arc/common/crash_collector.mojom

 // Copyright 2016 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.
 
-module arc;
+module arc.mojom;
 
 interface CrashCollectorHost {
   // Sends a dump for a non-native crash of the given |type|. The host reads
   // the dump from |pipe|, or rejects the dump by closing |pipe|. Note that
   // |type| is a string instead of an enum, because its value is not relevant
   // to the host: it only serves as a tag in the report.
   DumpCrash(string type, handle pipe);
 };
 
 interface CrashCollectorInstance {
   Init(CrashCollectorHost host_ptr);
 };