Force encryption migration if the device supports ARC.

chrome/browser/flag_descriptions.h

Index: chrome/browser/flag_descriptions.h
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index cbc45e8c05ebc702cf56c45b0b528273a0ba835d..dbf898e15b3cb4c7dc770ef8d70d3767a2a0b1ad 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -3160,6 +3160,13 @@ extern const char kEnableEhvInputName[];
 // opt-in IME menu.
 extern const char kEnableEhvInputDescription[];
 
+// Name of the about: flag for enabling encryption migratoin, which ensures the
+// user's cryptohome is encrypted by ext4 dircrypto instead of ecryptfs.
+extern const char kEnableEncryptionMigrationName[];
+
+// Description of the about: flag for enabling encryption migratoin.
+extern const char kEnableEncryptionMigrationDescription[];
+
 #endif  // #if defined(OS_CHROMEOS)
 
 }  // namespace flag_descriptions