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..68abb1b53c79c72332e0dd49679c363059a6481b
--- /dev/null
+++ b/content/browser/loader/resource_scheduler.cc
@@ -0,0 +1,216 @@
+// 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/public/browser/resource_controller.h"
+#include "content/public/browser/resource_throttle.h"
+#include "net/base/load_flags.h"
+#include "net/base/request_priority.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+
+namespace {
+
+ResourceScheduler::ClientId MakeClientId(int child_id, int route_id) {
+  return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;
+}
+
+}  // unnamed namespace
+
+class ResourceScheduler::ScheduledResourceRequest : public ResourceThrottle {
+ public:
+  ScheduledResourceRequest(const ClientId& client_id,
+                           const net::URLRequest& request,
+                           ResourceScheduler* scheduler)
+      : client_id_(client_id),
+        request_(request),
+        ready_(false),
+        deferred_(false),
+        scheduler_(scheduler) {
+  }
+
+  virtual ~ScheduledResourceRequest() {
+    scheduler_->RemoveRequest(this);
+  }
+
+  void Start() {
+    ready_ = true;
+    if (deferred_) {
+      controller()->Resume();
+    }
+  }
+
+  const ClientId& client_id() const { return client_id_; }
+  const net::URLRequest& url_request() const { return request_; }
+
+ private:
+  virtual void WillStartRequest(bool* defer) OVERRIDE {
+    deferred_ = *defer = !ready_;
+  }
+
+  ClientId client_id_;
+  const net::URLRequest& request_;
+  bool ready_;
+  bool deferred_;
+  ResourceScheduler* scheduler_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScheduledResourceRequest);
+};
+
+ResourceScheduler::ResourceScheduler() {
+  DetachFromThread();  // Construction happens on the main thread.
+}
+
+ResourceScheduler::~ResourceScheduler() {
+  DetachFromThread();  // Destruction happens on the main thread.
+}
+
+scoped_ptr<ResourceThrottle> ResourceScheduler::ScheduleRequest(
+    int child_id,
+    int route_id,
+    const 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));
+
+  if (route_id == 0 || !ContainsKey(client_map_, client_id)) {
+    // <a ping> requests don't belong to a specific page. Most tests don't call
+    // OnCreate et. al. as needed to register Clients either.
+    unowned_requests_.insert(request.get());
+    request->Start();
+    return request.PassAs<ResourceThrottle>();
+  }
+
+  Client* client = client_map_[client_id];
+  DCHECK(!client->has_closed);
+
+  // Treat synchronous requests as high priority.
+  bool is_low_priority = url_request.priority() < net::MEDIUM &&
+      !(url_request.load_flags() & net::LOAD_IGNORE_LIMITS);
+
+  if (is_low_priority && !client->in_flight_requests.empty() &&
+      !client->has_painted) {
+    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;
+  }
+
+  DCHECK(ContainsKey(client_map_, request->client_id()));
+  Client* client = client_map_[request->client_id()];
+  RequestSet::iterator it = client->in_flight_requests.find(request);
+  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) {
+        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->has_closed) {
+    if (client->in_flight_requests.empty()
+        && client->pending_requests.empty()) {
+      delete client;
+      client_map_.erase(request->client_id());
+    }
+  } else if (client->in_flight_requests.empty()) {
+    LoadPendingRequests(client);
+  }
+}
+
+void ResourceScheduler::OnCreate(int child_id, int route_id) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {
+    client_map_[client_id] = new Client;
+  }
+}
+
+void ResourceScheduler::OnNavigate(int child_id, int route_id) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {
+    return;

[darin (slow to review), 2012/12/18 21:09:56]

nit: What happens if a navigation occurs before OnCreate?  Should we be
asserting or trapping such conditions instead of just silently ignoring
OnNavigate?

+  }
+
+  Client* client = client_map_[client_id];
+  client->has_painted = false;
+}
+
+void ResourceScheduler::OnFirstPaint(int child_id, int route_id) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {
+    return;

[darin (slow to review), 2012/12/18 21:09:56]

ditto

+  }
+
+  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) {
+  DCHECK(CalledOnValidThread());
+  ClientId client_id = MakeClientId(child_id, route_id);
+  if (!ContainsKey(client_map_, client_id)) {
+    return;

[darin (slow to review), 2012/12/18 21:09:56]

ditto

+  }
+
+  Client* client = client_map_[client_id];
+  if (client->pending_requests.empty() && client->in_flight_requests.empty()) {
+    delete client;
+    client_map_.erase(client_id);
+  } else {
+    client->has_closed = true;
+  }
+}
+
+void ResourceScheduler::StartRequest(ScheduledResourceRequest* request,
+                                     Client* client) {
+  client->in_flight_requests.insert(request);
+  request->Start();
+}
+
+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),
+      has_closed(false) {
+}
+
+ResourceScheduler::Client::~Client() {
+}
+
+}  // namespace content