New Task Manager - Phase 1.1: Implement Browser Process Task Providing

chrome/browser/task_management/providers/task_provider.h

+// Copyright 2015 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_MANAGEMENT_PROVIDERS_TASK_PROVIDER_H_
+#define CHROME_BROWSER_TASK_MANAGEMENT_PROVIDERS_TASK_PROVIDER_H_
+
+#include "chrome/browser/task_management/providers/task_provider_observer.h"
+
+namespace task_management {
+
+// Defines the interface for task providers. A concrete task provider must be
+// able to collect all the tasks of a particular type which this provider
+// supports as well as track any tasks addition / removal. Once StartUpdating()
+// is called, the provider is responsible for notifying the observer about the
+// tasks it's tracking. The TaskProviders own the tasks they provide.
+class TaskProvider {
+ public:
+  TaskProvider();
+  virtual ~TaskProvider();
+
+  // Should return the task associated to the specified ids of a URLRequest,
+  // or nullptr if the desired task does not belong to this provider.
+  virtual Task* GetTaskOfUrlRequest(int origin_pid,

[Lei Zhang, 2015/04/01 22:47:51]

I looked in net/url_request/url_request.h and I still don't understand what
these parameters are. URLRequest doesn't refer to "pid" or "child" or "route" at
all.

[afakhry, 2015/04/03 01:51:01]

I agree it's confusing. You need to look at content::ResourceRequestInfo.

I added more comments to make it clearer.

[Lei Zhang, 2015/04/03 02:39:37]

Would it make sense to just say "the task associated with a ResourceRequestInfo"
and let the reader figure out ResourceRequestInfo maps to a given URLRequest. Is
it very important to mention URLRequest here?

[afakhry, 2015/04/03 16:04:27]

It's important to mention here that the only user of these interfaces will be
the task manager, this will not be exposed at all to the outside world.

That being said, I improved the comments a little bit.

+                                    int child_id,
+                                    int route_id) = 0;
+
+  void SetObserver(TaskProviderObserver* observer);

[Lei Zhang, 2015/04/01 22:47:51]

Given the impl, shouldn't this state:

- it's invalid to call SetObserver() when there's already an observer
- ClearObserver() cannot be called when there's no observer

[afakhry, 2015/04/03 01:51:01]

Done.

+  void ClearObserver();
+
+ protected:
+  // Used by concrete task providers to notify the observer of tasks addition/
+  // removal. These methods should only be called after StartUpdating() has been
+  // called and before StopUpdating() is called.
+  void NotifyObserverTaskAdded(Task* task) const;
+  void NotifyObserverTaskRemoved(Task* task) const;
+
+ private:
+  // This will be called once an observer is set for this provider. When it is
+  // called, the concrete provider must notify the observer of all pre-existing
+  // tasks as well as track new addition and terminations and notify the
+  // observer of these changes.
+  virtual void StartUpdating() = 0;
+
+  // This will be called once the observer is cleared, at which point the
+  // provider can stop tracking tasks addition / removal and can clear its own
+  // resources.
+  virtual void StopUpdating() = 0;
+
+  // We support only one single obsever which will be the sampler in this case.
+  TaskProviderObserver* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskProvider);
+};
+
+}  // namespace task_management
+
+#endif  // CHROME_BROWSER_TASK_MANAGEMENT_PROVIDERS_TASK_PROVIDER_H_