Add a ResourceScheduler to ResourceDispatcherHost.

content/browser/loader/resource_scheduler.cc

Index: content/browser/loader/resource_scheduler.cc
diff --git a/content/browser/loader/resource_scheduler.cc b/content/browser/loader/resource_scheduler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fdb9eb97e736837c0c1def4e4b98165ecd388455
--- /dev/null
+++ b/content/browser/loader/resource_scheduler.cc
@@ -0,0 +1,242 @@
+// 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/loader/resource_scheduler.h"
+
+#include "base/stl_util.h"
+#include "content/common/resource_messages.h"
+#include "content/browser/loader/resource_message_delegate.h"
+#include "content/public/browser/resource_controller.h"
+#include "content/public/browser/resource_throttle.h"
+#include "ipc/ipc_message_macros.h"
+#include "net/base/load_flags.h"
+#include "net/base/request_priority.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+
+// TODO(simonjam): This is arbitrary. Experiment.
+static const int kMaxNumNavigationsToTrack = 5;
+
+class ResourceScheduler::ScheduledResourceRequest
+    : public ResourceMessageDelegate,
+      public ResourceThrottle {
+ public:
+  ScheduledResourceRequest(const ClientId& client_id,
+                           net::URLRequest* request,
+                           ResourceScheduler* scheduler)
+      : ResourceMessageDelegate(request),
+        client_id_(client_id),
+        request_(request),
+        ready_(false),
+        deferred_(false),
+        scheduler_(scheduler) {
+  }
+
+  virtual ~ScheduledResourceRequest() {
+    scheduler_->RemoveRequest(this);
+  }
+
+  void Start() {
+    ready_ = true;
+    if (deferred_ && request_->status().is_success()) {
+      deferred_ = false;
+      controller()->Resume();
+    }
+  }
+
+  const ClientId& client_id() const { return client_id_; }
+  const net::URLRequest& url_request() const { return *request_; }
+
+ private:
+  // ResourceMessageDelegate interface:
+  virtual bool OnMessageReceived(const IPC::Message& message,
+                                 bool* message_was_ok) OVERRIDE {
+    bool handled = true;
+    IPC_BEGIN_MESSAGE_MAP_EX(ScheduledResourceRequest, message, *message_was_ok)
+      IPC_MESSAGE_HANDLER(ResourceHostMsg_DidChangePriority, DidChangePriority)
+      IPC_MESSAGE_UNHANDLED(handled = false)
+    IPC_END_MESSAGE_MAP_EX()
+    return handled;
+  }
+
+  // ResourceThrottle interface:
+  virtual void WillStartRequest(bool* defer) OVERRIDE {
+    deferred_ = *defer = !ready_;
+  }
+
+  void DidChangePriority(int request_id, net::RequestPriority new_priority) {
+    net::RequestPriority old_priority = request_->priority();
+    request_->set_priority(new_priority);
+    if (new_priority > old_priority) {
+      Start();
+    }
+  }
+
+  ClientId client_id_;
+  net::URLRequest* request_;
+  bool ready_;
+  bool deferred_;
+  ResourceScheduler* scheduler_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScheduledResourceRequest);
+};
+
+ResourceScheduler::ResourceScheduler()
+    : client_map_(kMaxNumNavigationsToTrack) {
+}
+
+ResourceScheduler::~ResourceScheduler() {
+  for (ClientMap::iterator it ALLOW_UNUSED = client_map_.begin();
+       it != client_map_.end(); ++it) {
+    DCHECK(it->second->pending_requests.empty());
+    DCHECK(it->second->in_flight_requests.empty());
+  }
+  DCHECK(unowned_requests_.empty());
+}
+
+scoped_ptr<ResourceThrottle> ResourceScheduler::ScheduleRequest(
+    int child_id,
+    int route_id,
+    net::URLRequest* url_request) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  scoped_ptr<ScheduledResourceRequest> request(
+      new ScheduledResourceRequest(client_id, url_request, this));
+
+  ClientMap::iterator it = client_map_.Get(client_id);
+  if (it == client_map_.end()) {
+    // There are several ways this could happen:
+    // 1. <a ping> requests don't have a route_id.
+    // 2. Most unittests don't send the IPCs needed to register Clients.
+    // 3. The tab is closed while a RequestResource IPC is in flight.
+    // 4. The tab hasn't navigated recently.
+    unowned_requests_.insert(request.get());
+    request->Start();
+    return request.PassAs<ResourceThrottle>();
+  }
+
+  Client* client = it->second;
+
+  bool is_synchronous = (url_request->load_flags() & net::LOAD_IGNORE_LIMITS) ==
+      net::LOAD_IGNORE_LIMITS;
+  bool is_low_priority =
+      url_request->priority() < net::MEDIUM && !is_synchronous;
+
+  if (is_low_priority && !client->in_flight_requests.empty() &&
+      !client->has_body) {
+    client->pending_requests.push_back(request.get());
+  } else {
+    StartRequest(request.get(), client);
+  }
+  return request.PassAs<ResourceThrottle>();
+}
+
+void ResourceScheduler::RemoveRequest(ScheduledResourceRequest* request) {
+  DCHECK(CalledOnValidThread());
+  if (ContainsKey(unowned_requests_, request)) {
+    unowned_requests_.erase(request);
+    return;
+  }
+
+  ClientMap::iterator client_it = client_map_.Get(request->client_id());
+  if (client_it == client_map_.end()) {
+    return;
+  }
+
+  Client* client = client_it->second;
+  RequestSet::iterator request_it = client->in_flight_requests.find(request);
+  if (request_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) {
+        client->pending_requests.erase(queue_it);
+        removed = true;
+        break;
+      }
+    }
+    DCHECK(removed);
+    DCHECK(!ContainsKey(client->in_flight_requests, request));
+  } else {
+    size_t erased = client->in_flight_requests.erase(request);
+    DCHECK(erased);
+  }
+
+  if (client->in_flight_requests.empty()) {
+    // Since the network is now idle, we may as well load some of the low
+    // priority requests.
+    LoadPendingRequests(client);
+  }
+}
+
+void ResourceScheduler::OnNavigate(int child_id, int route_id) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+
+  ClientMap::iterator it = client_map_.Get(client_id);
+  if (it == client_map_.end()) {
+    it = client_map_.Put(client_id, new Client(this));
+  }
+
+  Client* client = it->second;
+  client->has_body = false;
+}
+
+void ResourceScheduler::OnWillInsertBody(int child_id, int route_id) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  ClientMap::iterator it = client_map_.Get(client_id);
+  if (it == client_map_.end()) {
+    return;
+  }
+
+  Client* client = it->second;
+  if (!client->has_body) {
+    client->has_body = true;
+    LoadPendingRequests(client);
+  }
+}
+
+void ResourceScheduler::StartRequest(ScheduledResourceRequest* request,
+                                     Client* client) {
+  client->in_flight_requests.insert(request);
+  request->Start();
+}
+
+void ResourceScheduler::LoadPendingRequests(Client* client) {
+  while (!client->pending_requests.empty()) {
+    ScheduledResourceRequest* request = client->pending_requests.front();
+    client->pending_requests.erase(client->pending_requests.begin());
+    StartRequest(request, client);
+  }
+}
+
+void ResourceScheduler::RemoveClient(Client* client) {
+  LoadPendingRequests(client);
+  for (RequestSet::iterator it = client->in_flight_requests.begin();
+       it != client->in_flight_requests.end(); ++it) {
+    unowned_requests_.insert(*it);
+  }
+  client->in_flight_requests.clear();
+}
+
+ResourceScheduler::ClientId ResourceScheduler::MakeClientId(
+    int child_id, int route_id) {
+  return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;
+}
+
+ResourceScheduler::Client::Client(ResourceScheduler* scheduler)
+    : has_body(false),
+      scheduler_(scheduler) {
+}
+
+ResourceScheduler::Client::~Client() {
+  scheduler_->RemoveClient(this);
+  DCHECK(in_flight_requests.empty());
+  DCHECK(pending_requests.empty());
+}
+
+}  // namespace content