Does it seem sort of Microsoftish that Google uses an undocumented API to their own benefit without letting the rest of the community know?

There's a bit of difference: there's an open-source version of Chrome which presumably has a fully-commented source code implementation of this feature, together with a public bug tracker, etc.

The files are here: http://src.chromium.org/svn/trunk/src/chrome/browser/downloa...

drag_download_file.cc: http://src.chromium.org/svn/trunk/src/chrome/browser/downloa...

drag_download_file.h: http://src.chromium.org/svn/trunk/src/chrome/browser/downloa...

drag_download_util.cc: http://src.chromium.org/svn/trunk/src/chrome/browser/downloa...

drag_download_util.h: ttp://src.chromium.org/svn/trunk/src/chrome/browser/download/drag_download_util.h

In all likelihood, they wanted to be able to change the API as they see fit, and didn't want to have other people depending on an API that was changing rapidly. Can't fault them for that.

That's how Microsoft ended up with a bevy of undocumented API calls that still live today, with their internal software being among the largest offenders of using dated and problematic APIs.

The whole Drag and Drop API started life as a Microsoft only API. It's certainly not a bad thing that the Chromium team went ahead and did this, it's how innovation happens. Someone needs to take the first step.

The File API was the same, Mozilla went ahead and added it to Firefox and now it's in Chrome and soon other browsers will follow.