Task manager tracking RenderProcessHosts processes

chrome/browser/task_manager/providers/render_process_host_task_provider.h

+// Copyright 2017 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 CHROME_BROWSER_TASK_MANAGER_PROVIDERS_RENDER_PROCESS_HOST_TASK_PROVIDER_H_
+#define CHROME_BROWSER_TASK_MANAGER_PROVIDERS_RENDER_PROCESS_HOST_TASK_PROVIDER_H_
+
+#include <map>
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/task_manager/providers/task_provider.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/notification_service.h"
+
+namespace task_manager {
+
+class ChildProcessTask;
+
+// Defines a provider to provide possibly redundant tasks that represent RPHs
+// that are active. This can track interstitial pages and tracks RPHs that have
+// service workers still alive in them.

[Charlie Reis, 2017/08/02 18:39:14]

I think this is a little unclear to people who aren't familiar with the project.
 Maybe we can rephrase it to offer a bit more context?

My understanding is that this is currently a fallback provider that shows a row
for renderer processes when they exist but don't otherwise have tasks in them. 
For now, this is useful for showing things like interstitials and service
workers, but eventually those should get task providers of their own and this
provider won't provide anything shown to users.  (I could be wrong?)

It's also worth noting that this is only enabled if the
--task-manager-show-extra-renderers flag is passed.

I'm also unclear whether this currently shows anything if a process already has
tasks in it (e.g., if a tab and a service worker are in the same process, do we
get a line here for the service worker?  or only if there's no tabs?).  The
"possibly redundant" part made that unclear to me.  Can you clarify in the
comment?

[cburn, 2017/08/04 16:39:53]

I have fixed this in the follow on CL, where the behavior of this changes from
so that it will only show the "Renderer: " task row when there isn't a web
contents task that has the same Pid.

+class RenderProcessHostTaskProvider : public TaskProvider,
+                                      public content::NotificationObserver {
+ public:
+  RenderProcessHostTaskProvider();
+  ~RenderProcessHostTaskProvider() override;
+
+  // task_manager::TaskProvider:
+  Task* GetTaskOfUrlRequest(int origin_pid,
+                            int child_id,
+                            int route_id) override;
+
+  // content::NotificationObserver:
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override;
+
+ private:
+  // task_manager::TaskProvider:
+  void StartUpdating() override;
+  void StopUpdating() override;
+
+  // Creates a RenderProcessHostTask from the given |data| and notifies the
+  // observer of its addition.
+  void CreateTask(const int render_process_host_id);
+
+  // Deletes a RenderProcessHostTask whose |render_process_host_ID| is provided

[Charlie Reis, 2017/08/02 18:39:14]

nit: Update "ID" here as well.

[cburn, 2017/08/04 16:39:53]

Done.

+  // after notifying the observer of its deletion.
+  void DeleteTask(const int render_process_host_id);
+
+  std::map<int, std::unique_ptr<ChildProcessTask>> tasks_by_rph_id_;
+
+  // Object for registering notification requests.
+  content::NotificationRegistrar registrar_;
+
+  // Always keep this the last member of this class to make sure it's the
+  // first thing to be destructed.
+  base::WeakPtrFactory<RenderProcessHostTaskProvider> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderProcessHostTaskProvider);
+};
+
+}  // namespace task_manager
+
+#endif  // CHROME_BROWSER_TASK_MANAGER_PROVIDERS_RENDER_PROCESS_HOST_TASK_PROVIDER_H_