Fix -Wimplicit-fallthrough warnings for Chrome OS.

This CL was uploaded by git cl split.

R=alemate@chromium.org

Bug: 177475
Change-Id: I4b73b5ce51090fb9e2dd40adcf4117c95ee5a37a
Reviewed-on: https://chromium-review.googlesource.com/899448Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534487}

chromeos/login/auth/cryptohome_authenticator.cc

@@ -836,6 +836,7 @@ void CryptohomeAuthenticator::Resolve() {
       break;
     case CREATE_NEW:
       create_if_nonexistent = true;
+      FALLTHROUGH;
     case RECOVER_MOUNT:
       current_state_->ResetCryptohomeStatus();
       StartMount(current_state_->AsWeakPtr(),
@@ -854,10 +855,10 @@ void CryptohomeAuthenticator::Resolve() {
       break;
     case OFFLINE_LOGIN:
       VLOG(2) << "Offline login";
-    // Fall through.
+      FALLTHROUGH;
     case UNLOCK:
       VLOG(2) << "Unlock";
-    // Fall through.
+      FALLTHROUGH;
     case ONLINE_LOGIN:
       VLOG(2) << "Online login";
       task_runner_->PostTask(