Limit to only 10 image requests per page in ResourceScheduler.

content/browser/loader/resource_scheduler.h

Index: content/browser/loader/resource_scheduler.h
diff --git a/content/browser/loader/resource_scheduler.h b/content/browser/loader/resource_scheduler.h
index fa53c5b318f291d1d68a6054f4353d20958552b1..d9711134421c71273abead5be7807bddee68940c 100644
--- a/content/browser/loader/resource_scheduler.h
+++ b/content/browser/loader/resource_scheduler.h
@@ -7,15 +7,14 @@
 
 #include <map>
 #include <set>
-#include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "content/common/content_export.h"
-#include "content/public/browser/global_request_id.h"
+#include "net/base/priority_queue.h"
+#include "net/base/request_priority.h"
 
 namespace net {
 class URLRequest;
@@ -32,6 +31,11 @@ class ResourceThrottle;
 // 2. Notifications for renderer events, such as new tabs, navigation and
 //    painting.
 //
+// These input come from different threads, so they may not be in sync. The UI
+// thread is considered the authority on renderer lifetime, which means some
+// IPCs may be meaningless if they arrive after the UI thread signals a renderer
+// has been deleted.
+//
 // The ResourceScheduler tracks many Clients, which should correlate with tabs.
 // A client is uniquely identified by its child_id and route_id.
 //
@@ -56,12 +60,16 @@ class CONTENT_EXPORT ResourceScheduler : public base::NonThreadSafe {
   scoped_ptr<ResourceThrottle> ScheduleRequest(
       int child_id, int route_id, net::URLRequest* url_request);
 
+  // Signals from the UI thread, posted as tasks on the IO thread:
+
   // Called when a renderer is created.
   void OnClientCreated(int child_id, int route_id);
 
   // Called when a renderer is destroyed.
   void OnClientDeleted(int child_id, int route_id);
 
+  // Signals from IPC messages directly from the renderers:
+
   // Called when a client navigates to a new main document.
   void OnNavigate(int child_id, int route_id);
 
@@ -70,32 +78,41 @@ class CONTENT_EXPORT ResourceScheduler : public base::NonThreadSafe {
   void OnWillInsertBody(int child_id, int route_id);
 
  private:
+  class RequestQueue;
   class ScheduledResourceRequest;
-  friend class ScheduledResourceRequest;
   struct Client;
 
   typedef int64 ClientId;
   typedef std::map<ClientId, Client*> ClientMap;
-  typedef std::vector<ScheduledResourceRequest*> RequestQueue;
   typedef std::set<ScheduledResourceRequest*> RequestSet;
 
-  struct Client {
-    Client();
-    ~Client();
-
-    bool has_body;
-    RequestQueue pending_requests;
-    RequestSet in_flight_requests;
-  };
-
   // Called when a ScheduledResourceRequest is destroyed.
   void RemoveRequest(ScheduledResourceRequest* request);
 
   // Unthrottles the |request| and adds it to |client|.
   void StartRequest(ScheduledResourceRequest* request, Client* client);
 
-  // Calls StartRequest on all pending requests for |client|.
-  void LoadPendingRequests(Client* client);
+  // Update the queue position for |request|, possibly causing it to start
+  // loading.
+  //
+  // Queues are maintained for each priority level. When |request| is
+  // reprioritized, it will move to the end of the queue for that priority
+  // 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;
+
+  // Returns true if the request should start. This is the core scheduling
+  // algorithm.
+  bool 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);