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

net/url_request/url_request_throttler_manager.h

Index: net/url_request/url_request_throttler_manager.h
diff --git a/net/url_request/url_request_throttler_manager.h b/net/url_request/url_request_throttler_manager.h
index 427b42e9f2f87b062ed83e0418b81fee5b47ffc1..15a3eeddf77766b999203ad7726eaa812b5afb5a 100644
--- a/net/url_request/url_request_throttler_manager.h
+++ b/net/url_request/url_request_throttler_manager.h
@@ -24,6 +24,16 @@ namespace net {
 class BoundNetLog;
 class NetLog;
 
+class NET_EXPORT URLRequestThrottlerManagerDelegate {
+ public:
+  virtual ~URLRequestThrottlerManagerDelegate() {}
+
+  // Returns true if the URLRequestThrottlerManager may reject the
+  // request in question if it believe the server servicing the
+  // request to be overloaded or down.
+  virtual bool MayRejectRequest(URLRequest* request) = 0;

[eroman, 2012/06/05 05:30:25]

Same comment as earlier, please make |request| const. If delegates can cancel or
change the request, that complicates things. And I don't think it is necessary
here.

[Jói, 2012/06/05 16:39:14]

Done.

+};
+
 // Class that registers URL request throttler entries for URLs being accessed
 // in order to supervise traffic. URL requests for HTTP contents should
 // register their URLs in this manager on each request.
@@ -38,7 +48,8 @@ class NET_EXPORT URLRequestThrottlerManager
       public NetworkChangeNotifier::IPAddressObserver,
       public NetworkChangeNotifier::ConnectionTypeObserver {
  public:
-  URLRequestThrottlerManager();
+  explicit URLRequestThrottlerManager(
+      URLRequestThrottlerManagerDelegate* delegate);

[eroman, 2012/06/05 05:30:25]

Please describe ownership semantics (i.e. that |delegate| must remain alive). I
know this is following standard model, but always helps to document it anyway
for readers.

[Jói, 2012/06/05 16:39:14]

This concern goes away with the switch to NetworkDelegate, since I now retrieve
that when needed via the URLRequest's URLRequestContext.

   virtual ~URLRequestThrottlerManager();
 
   // Must be called for every request, returns the URL request throttler entry
@@ -113,6 +124,8 @@ class NET_EXPORT URLRequestThrottlerManager
   int GetNumberOfEntriesForTests() const { return url_entries_.size(); }
 
  private:
+  friend class URLRequestThrottlerEntry;
+
   // From each URL we generate an ID composed of the scheme, host, port and path
   // that allows us to uniquely map an entry to it.
   typedef std::map<std::string, scoped_refptr<URLRequestThrottlerEntry> >
@@ -141,10 +154,6 @@ class NET_EXPORT URLRequestThrottlerManager
   // Valid after construction.
   GURL::Replacements url_id_replacements_;
 
-  // Whether we would like to reject outgoing HTTP requests during the back-off
-  // period.
-  bool enforce_throttling_;
-
   // Certain tests do not obey the net component's threading policy, so we
   // keep track of whether we're being used by tests, and turn off certain
   // checks.
@@ -163,6 +172,8 @@ class NET_EXPORT URLRequestThrottlerManager
   // Valid once we've registered for network notifications.
   base::PlatformThreadId registered_from_thread_;
 
+  URLRequestThrottlerManagerDelegate* delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerManager);
 };