The Chromium issue tracker revealed a hidden gem today, a screenshot posted by a Google developer shows the debug icon of Android 6.0 Marshmallow. Android M's codename was already known but till now Android M Preview versions showed a different debug icon. 
(old Android M Developer Preview debug icon)
(Unreleased Android M version debug icon)
The new icon appears to be part of an unreleased Android M version running on a Nexus 9 (based on the screen resolution 2048 x 1536 of the original image). The new debug icon is more in line with the usual Android debug icons which usually feature two eyes and the two Android 'antennas'.
The screenshot appeared in a bug report where Google developers are talking about a new Chromium project called Mandoline. According to The Chromium website, "Mandoline is a project to explore an alternate to the Content layer in Chrome using Mojo Shell for application loading & management."
Mojo in its turn is described as "an effort to extract a common platform out of Chrome's renderer and plugin processes that can support multiple types of sandboxed content, such as HTML, Pepper, or NaCl."
We were also the first site that discovered the Android Lollipop debug icon.
