This is done on initialization of the Web Engine as this should
happen before any contexts and Direct 3D devices are created.

It makes D3D9 create a device with the D3DCREATE_MULTITHREADED
flag and makes D3D11 enable multithread protection using the
ID3D10Multithread interface.

Depends on the appropriate counterpart in QtANGLE.

Change-Id: I8204de2f8ebe993273ff9f11af55caacb1290e4e
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>