Passing parameters from the sample constructor allows us to test
ES3 functionality, as well as choose between D3D9 and 11.

BUG=angle:521

Change-Id: I7b9543b399450f62c5415654e8026a7c218b7e37
Reviewed-on: https://chromium-review.googlesource.com/193292Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>