Only store leading 13 bits of password hash.

chrome/browser/signin/local_auth.h

Index: chrome/browser/signin/local_auth.h
diff --git a/chrome/browser/signin/local_auth.h b/chrome/browser/signin/local_auth.h
index 2342a8142a2da6591238c44e2bba0a85401cd6b0..96ab6d002f7d955aff257b87d790b90fa8ec9646 100644
--- a/chrome/browser/signin/local_auth.h
+++ b/chrome/browser/signin/local_auth.h
@@ -24,6 +24,11 @@ void RegisterLocalAuthPrefs(user_prefs::PrefRegistrySyncable* registry);
 void SetLocalAuthCredentials(size_t profile_info_index,
                              const std::string& password);
 
+// For use by tests only to ensure backward compatibility.
+void SetLocalAuthCredentialsWithEncoding(size_t profile_info_index,
+                                         const std::string& password,
+                                         char encoding_version);
+
 void SetLocalAuthCredentials(const Profile* profile,
                              const std::string& password);
 
@@ -33,6 +38,9 @@ bool ValidateLocalAuthCredentials(size_t profile_info_index,
 bool ValidateLocalAuthCredentials(const Profile* profile,
                                   const std::string& password);
 
+// Return only the first |len_bits| bits of the string |str|.
+std::string TruncateStringByBits(const std::string& str, const size_t len_bits);
+
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SIGNIN_LOCAL_AUTH_H_