[Media Galleries] Lazily initialize the storage monitor.

chrome/browser/media_galleries/media_file_system_registry.cc

Index: chrome/browser/media_galleries/media_file_system_registry.cc
diff --git a/chrome/browser/media_galleries/media_file_system_registry.cc b/chrome/browser/media_galleries/media_file_system_registry.cc
index e659ad7431d11df61bf904f0e98077d6a3cead7e..87872ff18cd8e53d89ae8da460d5b5683b6331c0 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry.cc
@@ -435,7 +435,18 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
 
   Profile* profile =
       Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
-  MediaGalleriesPreferences* preferences = GetPreferences(profile);
+  GetPreferencesAsync(
+      profile, base::Bind(
+          &MediaFileSystemRegistry::GetMediaFileSystemsPostStorageMonitorInit,
+          weak_ptr_factory_.GetWeakPtr(),
+          rvh, extension, callback));
+}
+
+void MediaFileSystemRegistry::GetMediaFileSystemsPostStorageMonitorInit(
+    const content::RenderViewHost* rvh,
+    const extensions::Extension* extension,
+    const MediaFileSystemsCallback& callback,
+    MediaGalleriesPreferences* preferences) {
   MediaGalleryPrefIdSet galleries =
       preferences->GalleriesForExtension(*extension);
 
@@ -444,6 +455,8 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
     return;
   }
 
+  Profile* profile =
+      Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());

[vandebo (ex-Chrome), 2013/05/17 22:19:58]

Hmm, could the rvh have gone away while we were getting the preferences?

[Greg Billock, 2013/05/18 04:44:58]

I think so. Here's my current thinking.

We need to package this transaction in an object which is a
RenderViewHostObserver. We also need to make GetPreferencesAsync return a
pointer to a 
class MediaGalleriesPreferencesVendor {
  GetPreferences(Profile*) = 0;
}
which the registry can then implement.

I think that'll all work. It's a step more indirect and complex than this, but
encapsulating the transaction objects may make it tractable. :-/

   if (!ContainsKey(pref_change_registrar_map_, profile)) {
     PrefChangeRegistrar* pref_registrar = new PrefChangeRegistrar;
     pref_registrar->Init(profile->GetPrefs());
@@ -470,6 +483,36 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
                                       callback);
 }
 
+void MediaFileSystemRegistry::GetPreferencesAsync(
+    Profile* profile,
+    base::Callback<void(MediaGalleriesPreferences*)> callback) {
+  StorageMonitor* monitor = StorageMonitor::GetInstance();
+  // TODO(gbillock): Make sure tests all have a test storage monitor
+  // and eliminate the checks here and elsewhere.
+  if (!monitor) {
+    callback.Run(MediaGalleriesPreferencesFactory::GetForProfile(profile));
+    return;
+  }
+
+  if (monitor->IsInitialized()) {
+    callback.Run(GetPreferences(profile));
+    return;
+  }
+
+  monitor->Initialize(
+      base::Bind(&MediaFileSystemRegistry::OnStorageMonitorInitialized,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 profile, callback));
+
+  // TODO(gbillock): set a timeout here to bail out of init?
+}
+
+void MediaFileSystemRegistry::OnStorageMonitorInitialized(
+    Profile* profile,
+    base::Callback<void(MediaGalleriesPreferences*)> callback) {
+  callback.Run(GetPreferences(profile));
+}
+
 MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
     Profile* profile) {
   MediaGalleriesPreferences* preferences =
@@ -486,6 +529,7 @@ MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
   StorageMonitor* monitor = StorageMonitor::GetInstance();
   if (!monitor)
     return preferences;
+  DCHECK(monitor->IsInitialized());
   std::vector<StorageInfo> existing_devices = monitor->GetAttachedStorage();
   for (size_t i = 0; i < existing_devices.size(); i++) {
     if (!MediaStorageUtil::IsMediaDevice(existing_devices[i].device_id))
@@ -632,7 +676,8 @@ class MediaFileSystemRegistry::MediaFileSystemContextImpl
 };
 
 MediaFileSystemRegistry::MediaFileSystemRegistry()
-    : file_system_context_(new MediaFileSystemContextImpl(this)) {
+    : file_system_context_(new MediaFileSystemContextImpl(this)),
+      weak_ptr_factory_(this) {
   // StorageMonitor may be NULL in unit tests.
   StorageMonitor* monitor = StorageMonitor::GetInstance();
   if (monitor)