Adds missing USB events to the imageWriterPrivate API definition.

chrome/common/extensions/api/image_writer_private.idl

Index: chrome/common/extensions/api/image_writer_private.idl
diff --git a/chrome/common/extensions/api/image_writer_private.idl b/chrome/common/extensions/api/image_writer_private.idl
index 2dc3e3d07fe0022f8568ff9e33853df7a75b95a0..c60c2a9d73bc73588d17e0930c530015d2a55836 100644
--- a/chrome/common/extensions/api/image_writer_private.idl
+++ b/chrome/common/extensions/api/image_writer_private.idl
@@ -119,12 +119,20 @@
     // Fires periodically throughout the writing operation and at least once per
     // stage.
     static void onWriteProgress(ProgressInfo info);
+
     // Fires when the write operation has completely finished, such as all
     // devices being finalized and resources released.
     static void onWriteComplete();
+
     // Fires when an error occured during writing, passing the $ref:ProgressInfo
     // of the operation at the time the error occured.
     static void onWriteError(ProgressInfo info, DOMString error);
+
+    // Fires when a removable storage device is inserted.
+    static void onDeviceInserted(RemovableStorageDevice device);
+
+    // Fires when a removable storage device is removed.
+    static void onDeviceRemoved(RemovableStorageDevice device);
   };
 
 };