experiment with -Wimplicit-fallthrough

base/process/process_metrics_mac.cc

 // Copyright (c) 2013 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.
 
 #include "base/process/process_metrics.h"
 
 #include <mach/mach.h>
 #include <mach/mach_vm.h>
 #include <mach/shared_region.h>
 #include <sys/sysctl.h>
@@ skipping 148 matching lines @@
     if (info.share_mode == SM_COW && info.ref_count == 1)
       info.share_mode = SM_PRIVATE;
 
     switch (info.share_mode) {
       case SM_PRIVATE:
         private_pages_count += info.private_pages_resident;
         private_pages_count += info.shared_pages_resident;
         break;
       case SM_COW:
         private_pages_count += info.private_pages_resident;
-        // Fall through
+        FALLTHROUGH_INTENDED;
       case SM_SHARED:
         if (seen_objects.count(info.obj_id) == 0) {
           // Only count the first reference to this region.
           seen_objects.insert(info.obj_id);
           shared_pages_count += info.shared_pages_resident;
         }
         break;
       default:
         break;
     }
@@ skipping 136 matching lines @@
   kr = host_page_size(host, &page_size);
   if (kr) {
     DLOG(ERROR) << "Failed to fetch host page size.";
     return 0;
   }
 
   return (data.active_count * page_size) / 1024;
 }
 
 }  // namespace base