Remaining changes to build all code in src.git with -Wimplicit-fallthrough.

This CL was uploaded by git cl split.

R=pavely@chromium.org

Bug: 177475
Change-Id: Iec6559dc79f52f0b2e18b5197bdd75c70ab5d529
Reviewed-on: https://chromium-review.googlesource.com/891482Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533020}

components/browser_sync/profile_sync_service.cc

@@ -605,7 +605,7 @@ void ProfileSyncService::OnGetTokenFailure(
         UMA_HISTOGRAM_ENUMERATION("Sync.SyncAuthError", AUTH_ERROR_ENCOUNTERED,
                                   AUTH_ERROR_LIMIT);
       }
-      // Fallthrough.
+      FALLTHROUGH;
     }
     default: {
       if (error.state() != GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS) {