HTML Canvas rendering with ANGLE is very buggy

Rendering web pages that make use of the html canvas is very buggy with ANGLE on windows if the view is above a certain size.

An example can be found at http://www.casaportale.de/temp/touchandlearn

It will render alright if the window is rather small, but if the window is resized to about 2/3 of the screen, it will start not rendering certain layers / graphics, tear, flicker etc.

It works very well with desktop OpenGL.