On Wed, Jul 13, 2016 at 12:35 PM, Kevin Kofler <kevin.kofler@chello.at> wrote:
They are released with every bugfix release of Qt (5.6.1, 5.6.2, …). I
suppose that for really critical fixes, a separate advisory or even an
unscheduled Qt release would be made, as is done for all the other Qt
components.

...and upstream master is at 51.0.2704.106; which is current chrome stable.
It doesn't get much better than that... 

http://code.qt.io/cgit/qt/qtwebengine-chromium.git/log/?h=51-based