Add a ResourceScheduler to ResourceDispatcherHost.

content/browser/renderer_host/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_RENDERER_HOST_RESOURCE_SCHEDULER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_RESOURCE_SCHEDULER_H_
+
+#include <map>
+#include <set>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/global_request_id.h"
+
+namespace content {
+class ResourceLoader;
+
+// There is one ResourceScheduler, which is owned by the ResourceDispatcherHost.
+//
+// These are sources of input to the scheduler:
+// 1. Requests to load, cancel, or finish resources from the
+//    ResourceDispatcherHost.
+// 2. Notifications of renderer events from the ResourceSchedulerFilter.
+//
+// The ResourceScheduler tracks many Clients, which should correlate with tabs.
+// A client is uniquely identified by its child_id and route_id.
+//
+// Each Client may have many Requests in flight. Requests are uniquely
+// identified within a Client by their request_ids.
+//
+// The scheduling behavior mimicks WebKit's scheduler, which blocks fetching
+// low priority resources until the first paint has occurred. One exception is
+// if the client is not fetching anything else, low priority fetching begins
+// immediately.
+//
+// TODO(simonjam): This'd be CONTENT_EXPORT_PRIVATE if we had such a thing.

[willchan no longer on Chromium, 2012/10/25 19:44:49]

Why don't we have this? Aren't we trying to write more content unittests?

[James Simonsen, 2012/11/17 02:56:15]

Done.

+class CONTENT_EXPORT ResourceScheduler {
+ public:
+  ResourceScheduler();
+  ~ResourceScheduler();
+
+  // Called when the ResourceDispatcherHost is ready to load a resource.
+  void ScheduleLoad(int child_id,
+                    int route_id,
+                    int request_id,
+                    ResourceLoader* loader);
+
+  // Called when the ResourceDispatcherHost is done loading a resource.
+  void RemoveLoad(int child_id,
+                  int route_id,
+                  int request_id);
+
+  // These events are triggered by ViewHostMsgs.
+
+  // Called when a new client is created.
+  void OnCreate(int child_id, int route_id);
+
+  // Called when a client navigates to a new main document.
+  void OnNavigate(int child_id, int route_id);
+
+  // Called any time a client paints.
+  void OnPaint(int child_id, int route_id);
+
+  // Called when a client is destroyed.
+  void OnDestroy(int child_id, int route_id);
+
+ private:
+  struct Client;
+  struct Request;
+
+  typedef std::vector<Request> RequestQueue;
+  typedef std::set<int> RequestIdSet;
+  typedef std::map<int64, Client*> ClientMap;
+
+  struct Request {
+    int request_id;
+    ResourceLoader* loader;
+  };
+
+  struct Client {
+    Client();
+
+    bool has_painted;
+    RequestQueue pending_requests;
+    RequestIdSet in_flight_requests;
+  };
+
+  // Kicks off the loader for |request| and adds it to |client|.
+  void StartRequest(Request request, Client* client);
+
+  // Calls StartRequest on all pending requests for |client|.
+  void LoadPendingRequests(Client* client);
+
+  ClientMap client_map_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_RESOURCE_SCHEDULER_H_