[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 200b4f31a3647d81cc823b1e590cdf6b3c7c6414..6443fe66c898106ed86a1209f44460f463239fd4 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry.cc
@@ -37,6 +37,7 @@
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_view_host_observer.h"
 #include "content/public/browser/web_contents.h"
 #include "webkit/fileapi/file_system_types.h"
 #include "webkit/fileapi/isolated_context.h"
@@ -409,18 +410,68 @@ class ExtensionGalleriesHost
   DISALLOW_COPY_AND_ASSIGN(ExtensionGalleriesHost);
 };
 
+// This self-deleting transaction object contains the state needed to
+// asynchronously initialize the storage monitor if needed when an
+// extension calles |GetMediaFileSystemsForExtension|. Specifically,
+// it tracks if the RenderViewHost with which it was initialized was
+// destroyed, and if so, it never calls the callback.
+// When it receives the OnStorageMonitorInitialized callback, it deletes itself.
+class GetPreferencesTransaction : public content::RenderViewHostObserver {
+ public:
+  GetPreferencesTransaction(
+      content::RenderViewHost* rvh,
+      base::Closure callback)
+    : content::RenderViewHostObserver(rvh),
+      callback_(callback) {}
+  virtual ~GetPreferencesTransaction() {}
+
+  virtual void RenderViewHostDestroyed(content::RenderViewHost* rvh) OVERRIDE {
+    callback_.Reset();
+  }
+
+  void OnStorageMonitorInitialized() {
+    if (!callback_.is_null())
+      callback_.Run();
+
+    delete this;
+  }
+
+ private:
+  base::Closure callback_;
+};
+
 /******************
  * Public methods
  ******************/
 
 void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
-    const content::RenderViewHost* rvh,
+    content::RenderViewHost* rvh,
     const extensions::Extension* extension,
     const MediaFileSystemsCallback& callback) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  Profile* profile =
-      Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
+  // This object is self-deleting when it receives the callback
+  // from StorageMonitor::Initialize.
+  GetPreferencesTransaction* transaction = new GetPreferencesTransaction(
+      rvh,
+      base::Bind(
+          &MediaFileSystemRegistry::GetMediaFileSystemsPostInit,
+          weak_ptr_factory_.GetWeakPtr(),
+          rvh, extension, callback));
+  StorageMonitor* monitor = StorageMonitor::GetInstance();
+  if (monitor) {
+    monitor->Initialize(base::Bind(
+        &GetPreferencesTransaction::OnStorageMonitorInitialized,
+        base::Unretained(transaction)));
+  }
+}
+
+void MediaFileSystemRegistry::GetMediaFileSystemsPostInit(
+    const content::RenderViewHost* rvh,
+    const extensions::Extension* extension,
+    const MediaFileSystemsCallback& callback) {
+  Profile* profile = Profile::FromBrowserContext(
+      rvh->GetProcess()->GetBrowserContext());
   MediaGalleriesPreferences* preferences = GetPreferences(profile);
   MediaGalleryPrefIdSet galleries =
       preferences->GalleriesForExtension(*extension);
@@ -467,11 +518,12 @@ MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
   // once per profile.
   extension_hosts_map_[profile] = ExtensionHostMap();
 
-  // TODO(gbillock): Move this stanza to MediaGalleriesPreferences init code.
   // StorageMonitor may be NULL in unit tests.
+  // TODO(gbillock): Make sure all tests have a storage monitor and remove this.
   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 (!StorageInfo::IsMediaDevice(existing_devices[i].device_id))
@@ -616,7 +668,8 @@ 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)