Implement LoginDatabase on all platforms.

chrome/browser/password_manager/login_database_mac.cc

Index: chrome/browser/password_manager/login_database_mac.cc
diff --git a/chrome/browser/password_manager/login_database_mac.cc b/chrome/browser/password_manager/login_database_mac.cc
index 731f114ac22db8036627a4ac0f01005810012c8c..6e214ec049c0cae20cd63624bb30d8731a9c8de8 100644
--- a/chrome/browser/password_manager/login_database_mac.cc
+++ b/chrome/browser/password_manager/login_database_mac.cc
@@ -2,14 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/browser/password_manager/login_database_mac.h"
+#include "chrome/browser/password_manager/login_database.h"
 
-std::string LoginDatabaseMac::EncryptedString(const string16& plain_text)
-    const {
+// On the Mac, the LoginDatabase nulls out passwords, so that we can use the
+// rest of the database as a suplemental storage system to complement Keychain,
+// providing storage of fields Keychain doesn't allow.
+
+std::string LoginDatabase::EncryptedString(const string16& plain_text) const {
   return std::string();
 }
 
-string16 LoginDatabaseMac::DecryptedString(const std::string& cipher_text)
-    const {
+string16 LoginDatabase::DecryptedString(const std::string& cipher_text) const {
   return string16();
 }