EGLWindow: specify the device type only on d3d platform BUG=angleproject:892 Change-Id: I2dda3a8d15e58d15a401258a5a64c5783ea1a132 Reviewed-on: https://chromium-review.googlesource.com/269666 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>