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

net/url_request/url_request_throttler_entry_interface.h

Index: net/url_request/url_request_throttler_entry_interface.h
diff --git a/net/url_request/url_request_throttler_entry_interface.h b/net/url_request/url_request_throttler_entry_interface.h
index e46cd2aded2a4fa5c25d72b6a07ca58967eb4d2c..05a62feeacf11efc2df63988273ee185a92f2f68 100644
--- a/net/url_request/url_request_throttler_entry_interface.h
+++ b/net/url_request/url_request_throttler_entry_interface.h
@@ -15,6 +15,7 @@
 
 namespace net {
 
+class URLRequest;
 class URLRequestThrottlerHeaderInterface;
 
 // Interface provided on entries of the URL request throttler manager.
@@ -24,13 +25,13 @@ class NET_EXPORT URLRequestThrottlerEntryInterface
   URLRequestThrottlerEntryInterface() {}
 
   // Returns true when we have encountered server errors and are doing
-  // exponential back-off, unless the request has |load_flags| (from
-  // net/base/load_flags.h) that mean it is likely to be
-  // user-initiated.
+  // exponential back-off, unless the request has load flags that mean
+  // it is likely to be user-initiated, or the NetworkDelegate returns
+  // false for |CanThrottleRequest(request)|.
   //
   // URLRequestHttpJob checks this method prior to every request; it
   // cancels requests if this method returns true.
-  virtual bool ShouldRejectRequest(int load_flags) const = 0;
+  virtual bool ShouldRejectRequest(const URLRequest& request) const = 0;
 
   // Calculates a recommended sending time for the next request and reserves it.
   // The sending time is not earlier than the current exponential back-off