SystemInfo API: Fix SystemInfoEventRouter initialization code.

chrome/browser/extensions/api/system_info/system_info_api.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/extensions/api/system_info/system_info_api.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
@@ skipping 25 matching lines @@
 namespace system_storage = api::system_storage;
 
 namespace {
 
 #if defined(USE_ASH)
 bool IsDisplayChangedEvent(const std::string& event_name) {
   return event_name == system_display::OnDisplayChanged::kEventName;
 }
 #endif
 
+bool IsSystemStorageEvent(const std::string& event_name) {
+  return (event_name == system_storage::OnAttached::kEventName ||
+          event_name == system_storage::OnDetached::kEventName);
+}
+
 // Event router for systemInfo API. It is a singleton instance shared by
 // multiple profiles.
 class SystemInfoEventRouter : public gfx::DisplayObserver,
                               public RemovableStorageObserver {
  public:
   static SystemInfoEventRouter* GetInstance();
 
   SystemInfoEventRouter();
   virtual ~SystemInfoEventRouter();
 
@@ skipping 15 matching lines @@
   // processes cross multiple profiles.
   void DispatchEvent(const std::string& event_name,
                      scoped_ptr<base::ListValue> args);
 
   // Called to dispatch the systemInfo.display.onDisplayChanged event.
   void OnDisplayChanged();
 
   // Used to record the event names being watched.
   std::multiset<std::string> watching_event_set_;
 
+  bool has_storage_monitor_observer_;
+
   DISALLOW_COPY_AND_ASSIGN(SystemInfoEventRouter);
 };
 
 static base::LazyInstance<SystemInfoEventRouter>::Leaky
     g_system_info_event_router = LAZY_INSTANCE_INITIALIZER;
 
 // static
 SystemInfoEventRouter* SystemInfoEventRouter::GetInstance() {
   return g_system_info_event_router.Pointer();
 }
 
-SystemInfoEventRouter::SystemInfoEventRouter() {
-  StorageMonitor::GetInstance()->AddObserver(this);
-  StorageMonitor::GetInstance()->EnsureInitialized(base::Closure());
+SystemInfoEventRouter::SystemInfoEventRouter()
+    : has_storage_monitor_observer_(false) {
 }
 
 SystemInfoEventRouter::~SystemInfoEventRouter() {
-  if (StorageMonitor* storage_monitor = StorageMonitor::GetInstance())
-    storage_monitor->RemoveObserver(this);
+  if (has_storage_monitor_observer_) {
+    StorageMonitor* storage_monitor = StorageMonitor::GetInstance();
+    if (storage_monitor)
+      storage_monitor->RemoveObserver(this);
+  }
 }
 
 void SystemInfoEventRouter::AddEventListener(const std::string& event_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   watching_event_set_.insert(event_name);
   if (watching_event_set_.count(event_name) > 1)
     return;
 
   // For systemInfo.display event.
 #if defined(USE_ASH)
   if (IsDisplayChangedEvent(event_name))
     ash::Shell::GetScreen()->AddObserver(this);
 #endif
+
+  if (IsSystemStorageEvent(event_name)) {
+    if (!has_storage_monitor_observer_) {
+      has_storage_monitor_observer_ = true;
+      DCHECK(StorageMonitor::GetInstance()->IsInitialized());
+      StorageMonitor::GetInstance()->AddObserver(this);
+    }
+  }
 }
 
-void SystemInfoEventRouter::RemoveEventListener(
-    const std::string& event_name) {
+void SystemInfoEventRouter::RemoveEventListener(const std::string& event_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   std::multiset<std::string>::iterator it =
       watching_event_set_.find(event_name);
   if (it != watching_event_set_.end()) {
     watching_event_set_.erase(it);
     if (watching_event_set_.count(event_name) > 0)
       return;
   }
 
 #if defined(USE_ASH)
   if (IsDisplayChangedEvent(event_name))
     ash::Shell::GetScreen()->RemoveObserver(this);
 #endif
+
+  if (IsSystemStorageEvent(event_name)) {
+    const std::string& other_event_name =
+        (event_name == system_storage::OnDetached::kEventName) ?
+            system_storage::OnAttached::kEventName :
+            system_storage::OnDetached::kEventName;
+    if (watching_event_set_.count(other_event_name) == 0) {
+      StorageMonitor::GetInstance()->RemoveObserver(this);
+      has_storage_monitor_observer_ = false;
+    }
+  }
 }
 
 void SystemInfoEventRouter::OnRemovableStorageAttached(
     const StorageInfo& info) {
   StorageUnitInfo unit;
   systeminfo::BuildStorageUnitInfo(info, &unit);
   scoped_ptr<base::ListValue> args(new base::ListValue);
   args->Append(unit.ToValue().release());
   DispatchEvent(system_storage::OnAttached::kEventName, args.Pass());
 }
@@ skipping 26 matching lines @@
   scoped_ptr<base::ListValue> args(new base::ListValue());
   DispatchEvent(system_display::OnDisplayChanged::kEventName, args.Pass());
 }
 
 void SystemInfoEventRouter::DispatchEvent(const std::string& event_name,
                                           scoped_ptr<base::ListValue> args) {
   g_browser_process->extension_event_router_forwarder()->
       BroadcastEventToRenderers(event_name, args.Pass(), GURL());
 }
 
+void AddEventListener(const std::string& event_name) {
+  SystemInfoEventRouter::GetInstance()->AddEventListener(event_name);
+}
+
+void RemoveEventListener(const std::string& event_name) {
+  SystemInfoEventRouter::GetInstance()->RemoveEventListener(event_name);
+}
+
 }  // namespace
 
 static base::LazyInstance<ProfileKeyedAPIFactory<SystemInfoAPI> >
     g_factory = LAZY_INSTANCE_INITIALIZER;
 
 // static
 ProfileKeyedAPIFactory<SystemInfoAPI>* SystemInfoAPI::GetFactoryInstance() {
   return g_factory.Pointer();
 }
 
 SystemInfoAPI::SystemInfoAPI(Profile* profile) : profile_(profile) {
   EventRouter* router = ExtensionSystem::Get(profile_)->event_router();
   router->RegisterObserver(this, system_storage::OnAttached::kEventName);
   router->RegisterObserver(this, system_storage::OnDetached::kEventName);
   router->RegisterObserver(this, system_display::OnDisplayChanged::kEventName);
 }
 
 SystemInfoAPI::~SystemInfoAPI() {
 }
 
 void SystemInfoAPI::Shutdown() {
   ExtensionSystem::Get(profile_)->event_router()->UnregisterObserver(this);
 }
 
 void SystemInfoAPI::OnListenerAdded(const EventListenerInfo& details) {
-  SystemInfoEventRouter::GetInstance()->AddEventListener(details.event_name);
+  if (IsSystemStorageEvent(details.event_name)) {
+    StorageMonitor::GetInstance()->EnsureInitialized(
+        base::Bind(&AddEventListener, details.event_name));
+  } else {
+    AddEventListener(details.event_name);
+  }
 }
 
 void SystemInfoAPI::OnListenerRemoved(const EventListenerInfo& details) {
-  SystemInfoEventRouter::GetInstance()->RemoveEventListener(details.event_name);
+  if (IsSystemStorageEvent(details.event_name)) {
+    StorageMonitor::GetInstance()->EnsureInitialized(
+        base::Bind(&RemoveEventListener, details.event_name));
+  } else {
+    RemoveEventListener(details.event_name);
+  }
 }
 
 }  // namespace extensions