Code:    std::unique_ptr<net::test_server::HttpResponse> GetConfigResponse(
       const net::test_server::HttpRequest& request) {
     auto response = std::make_unique<net::test_server::BasicHttpResponse>();
     response->set_content(config_.SerializeAsString());
     response->set_content_type("text/plain");
    if (config_run_loop_)
      config_run_loop_->Quit();
    return response;
  }

Vulnerability Type: 
CWE ID: CWE-416
Summary: A use after free in PDFium in Google Chrome prior to 57.0.2987.98 for Mac, Windows, and Linux and 57.0.2987.108 for Android allowed a remote attacker to potentially exploit heap corruption via a crafted PDF file.
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}