Introduce a delegate to avoid hardcoding "chrome-extension" in net/.

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index 1fd4f8bd744e4543e4d27b165f9ea14b49c45b73..8491594f399d2dc2b286bdc48b0465d2cecd650d 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -307,18 +307,8 @@ void URLRequestHttpJob::StartTransactionInternal() {
     rv = request_->context()->http_transaction_factory()->CreateTransaction(
         &transaction_);
     if (rv == OK) {
-      // TODO(joi): The hard-coded check for "chrome-extension" is
-      // temporary (as of 2012/3/21), intended only to make sure this
-      // change (to throttle only requests originating from
-      // extensions) gets into M19. Right after the M19 branch point,
-      // I will sort this out in a more architecturally-sound way.
-      URLRequestThrottlerManager* manager =
-          request_->context()->throttler_manager();
-      DCHECK(!manager || throttling_entry_);
-      if (!manager ||
-          !manager->enforce_throttling() ||
-          request_->first_party_for_cookies().scheme() != "chrome-extension" ||
-          !throttling_entry_->ShouldRejectRequest(request_info_.load_flags)) {
+      if (!throttling_entry_ ||
+          !throttling_entry_->ShouldRejectRequest(*request_)) {
         rv = transaction_->Start(
             &request_info_, start_callback_, request_->net_log());
         start_time_ = base::TimeTicks::Now();