Prototype implementation of MediaImportHandler.

ui/file_manager/file_manager/background/js/background.js

Index: ui/file_manager/file_manager/background/js/background.js
diff --git a/ui/file_manager/file_manager/background/js/background.js b/ui/file_manager/file_manager/background/js/background.js
index 53e33d4f4cb37c6c998e90b9e4a1d749bc0c2012..6eda301fa5eceaf5b068db557ff06e9e9c96a3e5 100644
--- a/ui/file_manager/file_manager/background/js/background.js
+++ b/ui/file_manager/file_manager/background/js/background.js
@@ -83,6 +83,13 @@ function FileBrowserBackground() {
       function() { this.tryClose(); }.bind(this));
 
   /**
+   * Handles importing of user media (e.g. photos, videos) from removable
+   * devices.
+   * @type {MediaImportHandler}

[hirono, 2014/12/04 04:44:25]

@type {!MediaImporthandler}
@const

[Ben Kwa, 2014/12/04 19:53:01]

I fixed the nullable thing - thanks.
For the const part, the convention I'm accustomed to is to mark something as
const only if it's effectively immutable, which is not my intention (e.g. the
import task queue is going to go in there).

Also, I took the liberty of going through the rest of the FileBrowserBackground
initialization code and cleaning/fixing up some of the other type annotations,
PTAL.  Thanks!

[hirono, 2014/12/05 05:57:36]

Thank you for fixing them!

+   */
+  this.mediaImportHandler = new MediaImportHandler(this.fileOperationManager);
+
+  /**
    * Promise of string data.
    * @type {Promise}
    */