Create interface "EventPageTracker" for checking an extension's

suspend state and waking it up.
Make ProcessManager inherit from EventPageTracker.
Add new WakeExtension method to ProcessManager.

R=kalman@chromium.org,mfoltz@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1096313003

Cr-Commit-Position: refs/heads/master@{#327412}

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;
+
+// Tracks an extension's event page suspend state.
+class EventPageTracker {
+ public:
+  // Returns true if an extension's event page is active,
+  // or false if it is suspended.
+  virtual bool IsEventPageSuspended(const std::string& extension_id) = 0;
+
+  // Wakes an extension's event page from a suspended state and calls
+  // |callback| after it is reactivated.
+  //
+  // |callback| will be passed true if the extension was reactivated
+  // successfully, or false if an error occurred.
+  //
+  // Returns true if a wake operation was scheduled successfully,
+  // or false if the event page was already awake.
+  // Callback will be run asynchronously if true, and never run if false.
+  virtual bool WakeEventPage(const std::string& extension_id,
+                             const base::Callback<void(bool)>& callback) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_EVENT_PAGE_TRACKER_H_

extensions/browser/process_manager.cc

@@ -4,6 +4,8 @@
 
 #include "extensions/browser/process_manager.h"
 
+#include <vector>
+
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ -23,6 +25,7 @@
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extensions_browser_client.h"
+#include "extensions/browser/lazy_background_task_queue.h"
 #include "extensions/browser/notification_types.h"
 #include "extensions/browser/process_manager_delegate.h"
 #include "extensions/browser/process_manager_factory.h"
@@ -107,6 +110,11 @@ static void CreateBackgroundHostForExtensionLoad(
                                   BackgroundInfo::GetBackgroundURL(extension));
 }
 
+void PropagateExtensionWakeResult(const base::Callback<void(bool)>& callback,
+                                  extensions::ExtensionHost* host) {
+  callback.Run(host != nullptr);
+}
+
 }  // namespace
 
 struct ProcessManager::BackgroundPageData {
@@ -406,6 +414,23 @@ ExtensionHost* ProcessManager::GetBackgroundHostForExtension(
   return nullptr;
 }
 
+bool ProcessManager::IsEventPageSuspended(const std::string& extension_id) {
+  return GetBackgroundHostForExtension(extension_id) == nullptr;
+}
+
+bool ProcessManager::WakeEventPage(const std::string& extension_id,
+                                   const base::Callback<void(bool)>& callback) {
+  if (GetBackgroundHostForExtension(extension_id)) {
+    // Run the callback immediately if the extension is already awake.
+    return false;
+  }
+  LazyBackgroundTaskQueue* queue =
+      ExtensionSystem::Get(browser_context_)->lazy_background_task_queue();
+  queue->AddPendingTask(browser_context_, extension_id,
+                        base::Bind(&PropagateExtensionWakeResult, callback));
+  return true;
+}
+
 bool ProcessManager::IsBackgroundHostClosing(const std::string& extension_id) {
   ExtensionHost* host = GetBackgroundHostForExtension(extension_id);
   return (host && background_page_data_[extension_id].is_closing);

extensions/browser/process_manager.h

@@ -17,6 +17,7 @@
 #include "components/keyed_service/core/keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
+#include "extensions/browser/event_page_tracker.h"
 #include "extensions/browser/extension_registry_observer.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/view_type.h"
@@ -43,7 +44,8 @@ class ProcessManagerObserver;
 // track of split-mode extensions only.
 class ProcessManager : public KeyedService,
                        public content::NotificationObserver,
-                       public ExtensionRegistryObserver {
+                       public ExtensionRegistryObserver,
+                       public EventPageTracker {
  public:
   using ExtensionHostSet = std::set<extensions::ExtensionHost*>;
 
@@ -145,6 +147,11 @@ class ProcessManager : public KeyedService,
   void SetKeepaliveImpulseDecrementCallbackForTesting(
       const ImpulseCallbackForTesting& callback);
 
+  // EventPageTracker implementation.
+  bool IsEventPageSuspended(const std::string& extension_id) override;
+  bool WakeEventPage(const std::string& extension_id,
+                     const base::Callback<void(bool)>& callback) override;
+
   // Sets the time in milliseconds that an extension event page can
   // be idle before it is shut down; must be > 0.
   static void SetEventPageIdleTimeForTesting(unsigned idle_time_msec);

extensions/extensions.gypi

@@ -557,6 +557,7 @@
       'browser/error_map.h',
       'browser/event_listener_map.cc',
       'browser/event_listener_map.h',
+      'browser/event_page_tracker.h',
       'browser/event_router.cc',
       'browser/event_router.h',
       'browser/extension_error.cc',