Bug 1300297 - Ensure FxA device id is cleared on password change. r=markh

--HG--
extra : rebase_source : 8dd0d1110340525407accf0a6173e09275c90a67

services/fxaccounts/FxAccountsWebChannel.jsm

@@ -333,7 +333,9 @@ this.FxAccountsWebChannelHelpers.prototype = {
     // features (ie, new fields) - forcing the server to track a map of
     // versions to supported field names doesn't buy us much.
     // So we just remove field names we know aren't handled.
-    let newCredentials = {};
+    let newCredentials = {
+      deviceId: null
+    };
     for (let name of Object.keys(credentials)) {
       if (name == "email" || name == "uid" || FxAccountsStorageManagerCanStoreField(name)) {
         newCredentials[name] = credentials[name];

services/fxaccounts/tests/xpcshell/test_web_channel.js

@@ -414,6 +414,8 @@ add_task(function* test_helpers_change_password() {
           do_check_true(credentials.hasOwnProperty("email"));
           do_check_true(credentials.hasOwnProperty("uid"));
           do_check_true(credentials.hasOwnProperty("kA"));
+          do_check_true(credentials.hasOwnProperty("deviceId"));
+          do_check_null(credentials.deviceId);
           // "foo" isn't a field known by storage, so should be dropped.
           do_check_false(credentials.hasOwnProperty("foo"));
           wasCalled.updateUserAccountData = true;