Create interface "EventPageTracker" for checking an extension's

extensions/browser/event_page_tracker.h

Index: extensions/browser/event_page_tracker.h
diff --git a/extensions/browser/event_page_tracker.h b/extensions/browser/event_page_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..4934bdc3f2f84e6a9607daa2d230972156ec8794
--- /dev/null
+++ b/extensions/browser/event_page_tracker.h
@@ -0,0 +1,39 @@
+// 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
+// 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(
+      const std::string& extension_id) = 0;

[not at google - send to devlin, 2015/04/24 20:05:08]

GetEventPageForExtension? Just "background host" implies that it's all
background pages.

[Kevin Marshall, 2015/04/24 21:04:53]

This function is a pre-existing method in ProcessManager that has been promoted
to this interface. Do you want me to rename that method, or create a new one? If
I'm creating a new method for getting an extension's suspend state, I would
prefer to create a method with a simpler bool return value. It'd clean up the
interface quite a bit - no need for callers to reason about ExtensionHost
objects etc.

[not at google - send to devlin, 2015/04/24 21:20:43]

Sure, if you prefer a bool then makes sense to create a new interface which just
calls into GetBackgroundHostForExtension.

+
+  // Wakes an extension from a suspended state.
+  // |callback| is called with true if the extension was successfully loaded
+  //            or if it was already active; false if the extension failed
+  //            to load.
+  virtual void WakeExtension(const std::string& extension_id,
+                             const base::Callback<void(bool)>& callback) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_EVENT_PAGE_TRACKER_H_