Create interface "EventPageTracker" for checking an extension's

extensions/browser/event_page_tracker.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 EXTENSIONS_BROWSER_EVENT_PAGE_TRACKER_H_
+#define EXTENSIONS_BROWSER_EVENT_PAGE_TRACKER_H_
+
+#include <string>
+
+#include "base/callback.h"
+
+namespace extensions {
+
+class Extension;
+class ExtensionHost;
+
+// Defines a set of methods that can be used to track an extension's event page

[mark a. foltz, 2015/04/24 22:54:48]

Maybe:

Tracks an extension's event page suspend state, and wakes the event page on
demand.

[mark a. foltz, 2015/04/24 22:54:48]

Or just "Tracks an extension's..." as all classes define a set of methods :)

[Kevin M, 2015/04/27 19:45:38]

Acknowledged.

[Kevin M, 2015/04/27 19:45:38]

Done.

+// suspend state.
+class EventPageTracker {
+ public:
+  // Gets the ExtensionHost for the background page for an extension, or null if
+  // the extension isn't running or doesn't have a background page.
+  //
+  // A non-null return value indicates that an extension's event page is active;
+  // null indicates that it is suspended.
+  virtual ExtensionHost* GetBackgroundHostForExtension(

[mark a. foltz, 2015/04/24 22:54:48]

Why not have an IsSuspended(extension_id) that is a more readable form of 
(GBHFE != null)?

[Kevin M, 2015/04/27 19:45:37]

Done. I originally created this class to simply expose a subset of existing
ProcessManager methods, but it makes sense to have the methods be standalone.

+      const std::string& extension_id) = 0;
+
+  // Wakes an extension from a suspended state and calls |callback| after it is

[mark a. foltz, 2015/04/24 22:54:48]

As a nit, I would omit everything after |callback| since it seems like this
method doesn't guarantee wakeup.

[Kevin M, 2015/04/27 19:45:37]

How's this?

+  // reactivated. The callback is passed true if the extension was

[mark a. foltz, 2015/04/24 22:54:48]

s/The callback/|callback|/

[mark a. foltz, 2015/04/24 22:54:48]

s/reactivated/awoken/

[Kevin M, 2015/04/27 19:45:37]

Done.

+  // woken up successfully, or false if an error occurred.

[mark a. foltz, 2015/04/24 22:54:48]

If an error occurs, is the suspend/wake status of the event page known?

Maybe the callback should take two arguments:

- an enum { AWAKE, SUSPENDED, UNKNOWN } with the status
- an error boolean.

+  //
+  // Function returns true if a wake operation is scheduled, or false if the

[mark a. foltz, 2015/04/24 22:54:48]

s/Function//

[Kevin M, 2015/04/27 19:45:38]

Done.

+  //     extension is already active and does not require waking.

[mark a. foltz, 2015/04/24 22:54:48]

s/active/awake/ and omit the rest

[Kevin M, 2015/04/27 19:45:37]

Done.

+  virtual bool WakeExtension(const std::string& extension_id,
+                             const base::Callback<void(bool)>& callback) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_EVENT_PAGE_TRACKER_H_