Implement Mac Keychain migration algorithm.

chrome/browser/password_manager/password_store_mac_internal.h

Index: chrome/browser/password_manager/password_store_mac_internal.h
diff --git a/chrome/browser/password_manager/password_store_mac_internal.h b/chrome/browser/password_manager/password_store_mac_internal.h
index c8ea612e11d9ad9fca7d5b5e33507f71afdb65fd..47ec33c5d5187c2b2c28ec1c11fb9e78ed1406f4 100644
--- a/chrome/browser/password_manager/password_store_mac_internal.h
+++ b/chrome/browser/password_manager/password_store_mac_internal.h
@@ -139,6 +139,11 @@ bool FillPasswordFormFromKeychainItem(const AppleKeychain& keychain,
                                       autofill::PasswordForm* form,
                                       bool extract_password_data);
 
+// Returns true if |keychain_item| has the application-specific creator code in
+// its attributes.
+bool HasCreatorCode(const AppleKeychain& keychain,
+                    const SecKeychainItemRef& keychain_item);
+
 // Use FormMatchStrictness to configure which forms are considered a match by
 // FormsMatchForMerge:
 enum FormMatchStrictness {