Bug 1529495 - Output the result of ::GetLastError when CryptProtectData\CryptUnprotectData fails. r=MattN

Differential Revision: https://phabricator.services.mozilla.com/D20627

--HG--
extra : moz-landing-system : lando

toolkit/components/passwordmgr/OSCrypto_win.js

@@ -167,7 +167,7 @@ OSCrypto.prototype = {
                                                            null, null, FLAGS_NOT_SET,
                                                            outData.address());
     if (status === 0) {
-      throw new Error("decryptData failed: " + status);
+      throw new Error("decryptData failed: " + ctypes.winLastError);
     }
 
     // convert byte array to JS string.
@@ -213,7 +213,7 @@ OSCrypto.prototype = {
                                                          null, null, FLAGS_NOT_SET,
                                                          outData.address());
     if (status === 0) {
-      throw new Error("encryptData failed: " + status);
+      throw new Error("encryptData failed: " + ctypes.winLastError);
     }
 
     // convert byte array to JS string.