[Sync] Implement keystore migration support.

sync/protocol/proto_enum_conversions.cc

Index: sync/protocol/proto_enum_conversions.cc
diff --git a/sync/protocol/proto_enum_conversions.cc b/sync/protocol/proto_enum_conversions.cc
index 42d8ab54530f8ffeb13dbd1bfc2f9d5bfa69326c..2287b83a2b787679b824f1a329b0c2f701d10e3e 100644
--- a/sync/protocol/proto_enum_conversions.cc
+++ b/sync/protocol/proto_enum_conversions.cc
@@ -167,6 +167,20 @@ const char* GetFaviconTypeString(
   return "";
 }
 
+const char* PassphraseTypeString(
+    sync_pb::NigoriSpecifics::PassphraseType type) {
+  ASSERT_ENUM_BOUNDS(sync_pb::NigoriSpecifics, PassphraseType,
+                     IMPLICIT_PASSPHRASE, CUSTOM_PASSPHRASE);
+  switch (type) {
+    ENUM_CASE(sync_pb::NigoriSpecifics, IMPLICIT_PASSPHRASE);
+    ENUM_CASE(sync_pb::NigoriSpecifics, KEYSTORE_PASSPHRASE);
+    ENUM_CASE(sync_pb::NigoriSpecifics, FROZEN_IMPLICIT_PASSPHRASE);
+    ENUM_CASE(sync_pb::NigoriSpecifics, CUSTOM_PASSPHRASE);
+  }
+  NOTREACHED();
+  return "";
+}
+
 #undef ASSERT_ENUM_BOUNDS
 #undef ENUM_CASE