Make PassphraseType a "enum class" instead of "enum".

Make PassphraseType a "enum class" instead of "enum" which enable
forward declaration.

BUG=638963

Review-Url: https://codereview.chromium.org/2279713002
Cr-Commit-Position: refs/heads/master@{#415202}
diff --git a/chrome/browser/sync/profile_sync_service_android.cc b/chrome/browser/sync/profile_sync_service_android.cc
index ba991c2..01cdb6a 100644
--- a/chrome/browser/sync/profile_sync_service_android.cc
+++ b/chrome/browser/sync/profile_sync_service_android.cc
@@ -290,7 +290,7 @@
     JNIEnv* env,
     const JavaParamRef<jobject>&) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  return sync_service_->GetPassphraseType();
+  return static_cast<unsigned>(sync_service_->GetPassphraseType());
 }
 
 void ProfileSyncServiceAndroid::SetEncryptionPassphrase(