commit 070aeddba76c50d7b9394e9fb995d0cf2f7bfcd5
author Logan Hanks <logan@google.com> Wed Jun 20 10:24:35 2018 -0700
committer Logan Hanks <logan@google.com> Wed Jun 20 15:41:41 2018 -0700
tree cc94349b3a809bcb09d6703571a4401b00b0de17
parent e37c20e4a3b56991f04bb97d3de9c11d2f8c0c49

Fix excessive credential checks on fetch errors

This commit fixes a couple of bugs introduced in
I37db2f6e4dbf9632342ce853fae21f39d723a340. These bugs are particularly
noticeable if all fetches are failing for some reason. For example,
we discovered this problem on googlesource.com when a backend change
resulted in some users experiencing cross-origin 302 redirects on all
REST API calls (which materialized in PolyGerrit as fetch errors).

The specific bugs are:

1. The checkCredentials() method was called twice per failure (once
   immediately, and once via this.debounce).

2. The request made by checkCredentials() may raise a fetch error,
   which was not being caught, therefore triggering a loop of
   credential checks.

This commit adds tests against these scenarios, and simplifies the
fetch error credential checking logic to avoid these problems. Instead
of using debounce, a new boolean property makes checkCredentials() a
no-op if there is a checkCredentials() promise outstanding. An exception
handler is added to the checkCredentials() promise to interrupt any
[fetch error -> checkCredentials()] loop.

Change-Id: I868ced76a9816882e5705c2872706b824b6c1a95