[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..25595b66010d8211ca64558fcd84707444bdb0e1 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"
@@ -409,19 +410,67 @@ 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 eats the callback.
+// When it receives the OnPreferences callback, it deletes itself.
+class GetPreferencesTransaction : public content::RenderViewHostObserver {
+ public:
+  GetPreferencesTransaction(
+      content::RenderViewHost* rvh,
+      base::Callback<void(MediaGalleriesPreferences::Vendor*)> callback)
+    : content::RenderViewHostObserver(rvh),
+      callback_(callback) {}
+  virtual ~GetPreferencesTransaction() {}
+
+  virtual void RenderViewHostDestroyed(content::RenderViewHost* rvh) OVERRIDE {
+    callback_.Reset();
+  }
+
+  void OnPreferences(MediaGalleriesPreferences::Vendor* vendor) {
+    if (!callback_.is_null())
+      callback_.Run(vendor);
+
+    delete this;
+  }
+
+ private:
+  base::Callback<void(MediaGalleriesPreferences::Vendor*)> 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));
 
+  // This object is self-deleting when it receives the callback
+  // from GetPreferencesAsync.
+  GetPreferencesTransaction* transaction = new GetPreferencesTransaction(
+      rvh,
+      base::Bind(
+          &MediaFileSystemRegistry::GetMediaFileSystemsWithPreferences,
+          weak_ptr_factory_.GetWeakPtr(),
+          rvh, extension, callback));
+  GetPreferencesAsync(
+      base::Bind(&GetPreferencesTransaction::OnPreferences,
+                 base::Unretained(transaction)));
+}
+
+void MediaFileSystemRegistry::GetMediaFileSystemsWithPreferences(
+    const content::RenderViewHost* rvh,
+    const extensions::Extension* extension,
+    const MediaFileSystemsCallback& callback,
+    MediaGalleriesPreferences::Vendor* vendor) {
   Profile* profile =
       Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
-  MediaGalleriesPreferences* preferences = GetPreferences(profile);
+  MediaGalleriesPreferences* preferences = vendor->GetPreferences(profile);
   MediaGalleryPrefIdSet galleries =
       preferences->GalleriesForExtension(*extension);
 
@@ -456,6 +505,33 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
                                       callback);
 }
 
+void MediaFileSystemRegistry::GetPreferencesAsync(
+    base::Callback<void(MediaGalleriesPreferences::Vendor*)> 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(this);
+    return;
+  }
+
+  if (monitor->IsInitialized()) {
+    callback.Run(this);
+    return;
+  }
+
+  monitor->Initialize(
+      base::Bind(&MediaFileSystemRegistry::OnStorageMonitorInitialized,
+                 weak_ptr_factory_.GetWeakPtr(), callback));
+
+  // TODO(gbillock): set a timeout here to bail out of init?
+}
+
+void MediaFileSystemRegistry::OnStorageMonitorInitialized(
+    base::Callback<void(MediaGalleriesPreferences::Vendor*)> callback) {
+  callback.Run(this);
+}
+
 MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
     Profile* profile) {
   MediaGalleriesPreferences* preferences =
@@ -468,10 +544,12 @@ MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
   extension_hosts_map_[profile] = ExtensionHostMap();
 
   // TODO(gbillock): Move this stanza to MediaGalleriesPreferences init code.
+  // Or better, just make sure tests have a storage monitor.
   // StorageMonitor may be NULL in unit tests.
   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 +694,8 @@ 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)