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

components/sync/engine/sync_string_conversions.cc

Index: components/sync/engine/sync_string_conversions.cc
diff --git a/components/sync/engine/sync_string_conversions.cc b/components/sync/engine/sync_string_conversions.cc
index dfd9e2414a12f13f4474001bcfd41baf9c48d51c..bdcc6413ffc9fff6ddd0ba8699b65e4d6fbc8c92 100644
--- a/components/sync/engine/sync_string_conversions.cc
+++ b/components/sync/engine/sync_string_conversions.cc
@@ -35,10 +35,10 @@ const char* PassphraseRequiredReasonToString(PassphraseRequiredReason reason) {
 
 const char* PassphraseTypeToString(PassphraseType type) {
   switch (type) {
-    ENUM_CASE(IMPLICIT_PASSPHRASE);
-    ENUM_CASE(KEYSTORE_PASSPHRASE);
-    ENUM_CASE(FROZEN_IMPLICIT_PASSPHRASE);
-    ENUM_CASE(CUSTOM_PASSPHRASE);
+    ENUM_CASE(PassphraseType::IMPLICIT_PASSPHRASE);
+    ENUM_CASE(PassphraseType::KEYSTORE_PASSPHRASE);
+    ENUM_CASE(PassphraseType::FROZEN_IMPLICIT_PASSPHRASE);
+    ENUM_CASE(PassphraseType::CUSTOM_PASSPHRASE);
     default:
       NOTREACHED();
       return "INVALID_PASSPHRASE_TYPE";