DynamicHLSL encapsulates all HLSL generation we need outside the
the shader translator, such as for linking between input and output
stages and point sprite geometry shaders.

BUG=angle:560
Change-Id: Ib5079aa102000a7c37b166bcbe26b09cc82f8932
Reviewed-on: https://chromium-review.googlesource.com/185191Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>