Fix assertion logic in SmbCredentialDialog

- Previously the assertion logic in SmbCredentialDialog treated 0 as an
invalid mount_id. Since 0 is a valid mount_id, we want to ensure that
the assert is only verifying that mount_id is a number.


Bug: 928933
Change-Id: I165f6696252265a66af7de488a624d6fc41e5d22
Reviewed-on: https://chromium-review.googlesource.com/c/1455498
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Auto-Submit: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629453}

chrome/browser/resources/chromeos/smb_shares/smb_credentials_dialog.js

@@ -44,7 +44,7 @@ Polymer({
     var args = JSON.parse(dialogArgs);
     assert(args);
     assert(args.path);
-    assert(args.mid);
+    assert(typeof args.mid === 'number');
     this.sharePath_ = args.path;
     this.mountId_ = args.mid;