Add the Sync.PassphraseType histogram.

sync/internal_api/public/sync_encryption_handler.h

Index: sync/internal_api/public/sync_encryption_handler.h
diff --git a/sync/internal_api/public/sync_encryption_handler.h b/sync/internal_api/public/sync_encryption_handler.h
index cd1cfc04f02c498f5972abab79dd363584ce3cdf..a939aa83634a7802d22919b1e9aa54a1708fdd13 100644
--- a/sync/internal_api/public/sync_encryption_handler.h
+++ b/sync/internal_api/public/sync_encryption_handler.h
@@ -40,6 +40,8 @@ enum PassphraseType {
   CUSTOM_PASSPHRASE = 3,               // User-provided passphrase.
 };
 
+const int PASSPHRASE_TYPE_SIZE = 4;

[Alexei Svitkine (slow), 2014/12/04 19:57:06]

Usually, this is put inside the enum at the end, so it automatically grows as
new entries are added.

If there's a good reason why you'd rather not do that, I'm ok with that. If not,
please follow the convention.

[maxbogue, 2014/12/04 21:14:24]

I thought about doing that, but it might affect code that depends on those being
the only possible values for that enum (thinking switch statements). Nicolas,
have any thoughts on this?

[Nicolas Zea, 2014/12/05 00:53:19]

I'm fine with adding a NUM_PASSPHRASE_TYPES enum, but not sure if you'll need to
update any switch statements.

[maxbogue, 2014/12/05 18:58:59]

Done. It all compiled.

+
 // Enum used to distinguish which bootstrap encryption token is being updated.
 enum BootstrapTokenType {
   PASSPHRASE_BOOTSTRAP_TOKEN,