Fix GN build with missing ShaderVars.cpp. Change-Id: I29be6cdda643f83a40a6adc9b76153667aafcc51 Reviewed-on: https://chromium-review.googlesource.com/211400 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Zhenyao Mo <zmo@chromium.org>