Add a cap of six in-flight requests per host to the ResourceScheduler

content/browser/loader/resource_scheduler.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_
 #define CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_
 
 #include <map>
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "content/common/content_export.h"
 #include "net/base/priority_queue.h"
 #include "net/base/request_priority.h"
 
 namespace net {
+class HostPortPair;
 class URLRequest;
 }
 
 namespace content {
 class ResourceThrottle;
 
 // There is one ResourceScheduler. All renderer-initiated HTTP requests are
 // expected to pass through it.
 //
 // There are two types of input to the scheduler:
@@ skipping 70 matching lines @@
   // level.
   void ReprioritizeRequest(ScheduledResourceRequest* request,
                            net::RequestPriority new_priority);
 
   // Attempts to load any pending requests in |client|, based on the
   // results of ShouldStartRequest().
   void LoadAnyStartablePendingRequests(Client* client);
 
   // Returns the number of requests with priority < LOW that are currently in
   // flight.
-  size_t GetNumDelayableRequestsInFlight(Client* client) const;
+  void GetNumDelayableRequestsInFlight(
+      Client* client,
+      const net::HostPortPair& active_request_host,
+      size_t* total_delayable,
+      size_t* total_for_active_host) const;
+
+  enum ShouldStartReqResult {
+    DO_NOT_START_REQUEST_AND_STOP_SEARCHING = -2,
+    DO_NOT_START_REQUEST_AND_KEEP_SEARCHING = -1,
+    START_REQUEST = 1,
+  };
 
   // Returns true if the request should start. This is the core scheduling
   // algorithm.
-  bool ShouldStartRequest(ScheduledResourceRequest* request,
-                          Client* client) const;
+  ShouldStartReqResult ShouldStartRequest(ScheduledResourceRequest* request,
+                                          Client* client) const;
 
   // Returns the client ID for the given |child_id| and |route_id| combo.
   ClientId MakeClientId(int child_id, int route_id);
 
   ClientMap client_map_;
   RequestSet unowned_requests_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_RESOURCE_SCHEDULER_H_