Reland https://codereview.chromium.org/1271593002/ which was reverted

net/url_request/url_request_simple_job.cc

Index: net/url_request/url_request_simple_job.cc
diff --git a/net/url_request/url_request_simple_job.cc b/net/url_request/url_request_simple_job.cc
index 2f2fb875a2c7668f827d5e2e98436e344bd2951b..2fdbef4049ad0db86e25562b041ace700c20a0f5 100644
--- a/net/url_request/url_request_simple_job.cc
+++ b/net/url_request/url_request_simple_job.cc
@@ -48,6 +48,11 @@ void URLRequestSimpleJob::Start() {
       base::Bind(&URLRequestSimpleJob::StartAsync, weak_factory_.GetWeakPtr()));
 }
 
+void URLRequestSimpleJob::Kill() {
+  weak_factory_.InvalidateWeakPtrs();
+  URLRangeRequestJob::Kill();
+}
+
 bool URLRequestSimpleJob::GetMimeType(std::string* mime_type) const {
   *mime_type = mime_type_;
   return true;