Add API to get a folder's size.

chrome/common/extensions/api/file_manager_private.idl

Index: chrome/common/extensions/api/file_manager_private.idl
diff --git a/chrome/common/extensions/api/file_manager_private.idl b/chrome/common/extensions/api/file_manager_private.idl
index fef52e9315c013a05d6fff747551f23beb21ab54..1cd0cbb8829b769bd7ab463ff9c95a4a51de9bdb 100644
--- a/chrome/common/extensions/api/file_manager_private.idl
+++ b/chrome/common/extensions/api/file_manager_private.idl
@@ -969,6 +969,13 @@ interface Functions {
   static void executeCustomAction([instanceof=Entry] object[] entries,
                                   DOMString actionId,
                                   SimpleCallback callback);
+
+  // Get the total size of a directory.
+  // |entry| Entry of the target directory.
+  // |callback|
+  [nocompile]
+  static void getDirectorySize([instanceof=DirectoryEntry] object entry,
+                               SimpleCallback callback);

[fukino, 2016/08/30 05:17:06]

We need to receive the directory size, so please define a callback type for this
method instead of using SimpleCallback.

[harukam, 2016/08/30 06:33:42]

Acknowledged.

 };
 
 interface Events {