Add VLOGs for authentication failure

We're trying to track down the cause of some login flake in tast
tests, which is inhibited by not being able to see the error response
from the gaia servers.

Add some VLOG statements to GenerateAuthError to record the exact
error type and response. These will be enabled in some tast tests.

Bug: 1166530
Change-Id: Ie9fc408f49e406ffc3790a7ec5dc65bf1eedf2a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2639338Reviewed-by: Alex Ilin <alexilin@chromium.org>
Reviewed-by: Shuhei Takahashi <nya@chromium.org>
Commit-Queue: Fergus Dall <sidereal@google.com>
Cr-Commit-Position: refs/heads/master@{#845524}

google_apis/gaia/gaia_auth_fetcher.cc

@@ -983,6 +983,10 @@ void GaiaAuthFetcher::StartGetCheckConnectionInfo() {
 GoogleServiceAuthError GaiaAuthFetcher::GenerateAuthError(
     const std::string& data,
     net::Error net_error) {
+  VLOG(1) << "Got authentication error";
+  VLOG(1) << "net_error: " << net::ErrorToString(net_error);
+  VLOG(1) << "response body: " << data;
+
   if (net_error != net::OK) {
     if (net_error == net::ERR_ABORTED) {
       return GoogleServiceAuthError(GoogleServiceAuthError::REQUEST_CANCELED);