Code:  bool DataReductionProxyConfig::IsFetchInFlight() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return warmup_url_fetcher_->IsFetchInFlight();
 }

Commit Message: Disable all DRP URL fetches when holdback is enabled

Disable secure proxy checker, warmup url fetcher
and client config fetch when the client is in DRP
(Data Reduction Proxy) holdback.

This CL does not disable pingbacks when client is in the
holdback, but the pingback code is going away soon.

Change-Id: Icbb59d814d1452123869c609e0770d1439c1db51
Bug: 984964
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1709965
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679649}
CWE ID: CWE-416
 bool DataReductionProxyConfig::IsFetchInFlight() const {
   DCHECK(thread_checker_.CalledOnValidThread());

  if (!warmup_url_fetcher_)
    return false;
   return warmup_url_fetcher_->IsFetchInFlight();
 }
