AI 147423: Provide a hook to notify remote stores that local stores are set up.

BUG=1807499

Automated import of CL 147423

src/com/android/email/MessagingController.java

@@ -246,6 +246,9 @@ public class MessagingController implements Runnable {
                         }
 
                         localFolders = localStore.getPersonalNamespaces();
+                        
+                        // Signal the remote store that it can now use folder-based callbacks
+                        store.localFolderSetupComplete();
 
                         for (MessagingListener l : mListeners) {
                             l.listFolders(account, localFolders);

src/com/android/email/mail/Store.java

@@ -192,6 +192,20 @@ public abstract class Store {
     public abstract Folder getFolder(String name) throws MessagingException;
 
     public abstract Folder[] getPersonalNamespaces() throws MessagingException;
+    
+    /**
+     * This function will be called after the messaging controller has called 
+     * getPersonalNamespaces() and has created a matching set of LocalFolder objects.  This can
+     * be used as a trigger for the store to write back any folder-specific persistent data using
+     * callbacks.
+     * 
+     * This is not abstract because most stores do not require this functionality and do not
+     * need to implement it.
+     */
+    @SuppressWarnings("unused")
+    public void localFolderSetupComplete() throws MessagingException {
+        // Do nothing - return immediately
+    }
 
     public abstract void checkSettings() throws MessagingException;