Add a ResourceScheduler to ResourceDispatcherHost.

content/browser/renderer_host/resource_scheduler.cc

+// 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.
+
+#include "content/browser/renderer_host/resource_scheduler.h"
+
+#include "base/stl_util.h"
+#include "content/browser/renderer_host/resource_loader.h"
+#include "net/base/request_priority.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+
+namespace {
+
+int64 MakeClientId(int child_id, int route_id) {
+  return static_cast<int64>(child_id) << 32 | route_id;

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

I don't memorize the order of operations between << and |, please add a
parentheses to clarify :)

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

Done.

+}
+
+}  // unnamed namespace
+
+ResourceScheduler::ResourceScheduler() {
+}
+
+ResourceScheduler::~ResourceScheduler() {
+}
+
+void ResourceScheduler::ScheduleLoad(int child_id,
+                                     int route_id,
+                                     int request_id,
+                                     ResourceLoader* loader) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {

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

I don't understand this. If the client doesn't exist, then we always start the
request? Is that because it's the first request for the client and we never want
to hold it back? What if we are loading a bunch of tabs in the background?

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

Turns out these were the <a ping> requests. I added a comment and explicitly
handle them.

+    loader->StartRequest();
+    return;
+  }
+
+  Client* client = client_map_[client_id];
+  Request request = { request_id, loader };
+  if (loader->request()->priority() < net::MEDIUM &&
+      !client->in_flight_requests.empty() && !client->has_painted) {
+    client->pending_requests.push_back(request);
+    return;
+  }
+
+  StartRequest(request, client);
+}
+
+void ResourceScheduler::RemoveLoad(int child_id, int route_id, int request_id) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {

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

Why would this ever happen? Is this a bug? Should it be NOTREACHED()?

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

When a tab goes away suddenly the OnDestroy() comes in first, then the
ResourceDispatcher clears out all of that tab's requests. I've explicitly
handled that case now.

+    return;
+  }
+
+  Client* client = client_map_[client_id];
+  RequestIdSet::iterator it = client->in_flight_requests.find(request_id);
+  if (it == client->in_flight_requests.end()) {
+    bool removed = false;
+    RequestQueue::iterator queue_it;
+    for (queue_it = client->pending_requests.begin();
+         queue_it != client->pending_requests.end(); ++queue_it) {
+      if (queue_it->request_id == request_id) {
+        client->pending_requests.erase(queue_it);
+        removed = true;
+        break;
+      }
+    }
+    DCHECK(removed);
+    DCHECK(!ContainsKey(client->in_flight_requests, request_id));
+  } else {
+    bool erased = client->in_flight_requests.erase(request_id);
+    DCHECK(erased);
+  }
+
+  if (client->in_flight_requests.empty()) {
+    LoadPendingRequests(client);
+  }
+}
+
+void ResourceScheduler::OnCreate(int child_id, int route_id) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  DCHECK(!ContainsKey(client_map_, client_id));
+  client_map_[client_id] = new Client;
+}
+
+void ResourceScheduler::OnNavigate(int child_id, int route_id) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  DCHECK(ContainsKey(client_map_, client_id));
+  Client* client = client_map_[client_id];
+  client->has_painted = false;
+}
+
+void ResourceScheduler::OnPaint(int child_id, int route_id) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  DCHECK(ContainsKey(client_map_, client_id));
+  Client* client = client_map_[client_id];
+  if (!client->has_painted) {
+    client->has_painted = true;
+    LoadPendingRequests(client);
+  }
+}
+
+void ResourceScheduler::OnDestroy(int child_id, int route_id) {
+  int64 client_id = MakeClientId(child_id, route_id);
+  bool erased = client_map_.erase(client_id);
+  DCHECK(erased);
+}
+
+void ResourceScheduler::StartRequest(Request request, Client* client) {
+  client->in_flight_requests.insert(request.request_id);
+  request.loader->StartRequest();
+}
+
+void ResourceScheduler::LoadPendingRequests(Client* client) {
+  RequestQueue::iterator it;
+  for (it = client->pending_requests.begin();
+       it != client->pending_requests.end(); ++it) {
+    StartRequest(*it, client);
+  }
+  client->pending_requests.clear();
+}
+
+ResourceScheduler::Client::Client()
+    : has_painted(false) {
+}
+
+}  // namespace content