Allow the consumer of storage monitor to register callback when the initialization is completed.

chrome/browser/storage_monitor/storage_monitor.h

Index: chrome/browser/storage_monitor/storage_monitor.h
diff --git a/chrome/browser/storage_monitor/storage_monitor.h b/chrome/browser/storage_monitor/storage_monitor.h
index 7eab0b7743b925d9b3fffa009623e946c32b496d..b90a6fbf773fcaccde96d912284eae0cce335559 100644
--- a/chrome/browser/storage_monitor/storage_monitor.h
+++ b/chrome/browser/storage_monitor/storage_monitor.h
@@ -64,6 +64,12 @@ class StorageMonitor {
   // somewhat shorter than a process Singleton.
   static StorageMonitor* GetInstance();
 
+  // Register a callback to be called when the initialization is completed, e.g.
+  // the metdata of storage devices are already retrieved. If the initialization
+  // is already completed, the provided callback will be invoked immediately
+  // with the current calling stack.
+  void RegisterInitCompletedCallback(base::Closure callback);

[wrong vandebo, 2013/05/29 15:08:35]

I don't understand why you would want this method.  If you want to register an
observer, then you presumably want that observer to be called.  The observer
won't be called until initialization is complete.

[Hongbo Min, 2013/05/29 15:15:39]

Since the RemovableStorageObserver only gets notified when a storage is
attached/detached, the thing I want to do is, I need a way to tell me when it is
safe to call GetAttachedStorage/GetAllAvailableStorages to return the correct
results. 

Without this method, the consumer of StorageMonitor doesn't know the proper
timing of calling GetAttachedStorage at all.

Also, it might be wrong to invoke Initialize with a callback since the Init
method will be called by Initialize again.

+
   // Initialize the storage monitor. The provided callback, if non-null,
   // will be called when initialization is complete. If initialization has
   // already completed, this callback will be invoked within the calling stack.