Aura, which replaces GTK+, is used to draw the bulk of the Chrome UI on screen, including menus and window frames (and yes, it works fine with both locally integrated and global menus).
An accelerated interface, Aura is better able to leverage GPU features in Chrome/Chromium on Linux than GTK+ builds. Notably, it is able to use OpenGL on a per-window rather than per-tab basis.
Its arrival also brings additional features to the desktop, including the Chrome Notification Centre, an optional App Launcher and support for displaying select Google Now cards.
[Source: OMG! Ubuntu!]