This change makes it so that when we need to recompile a program on a
draw call, we also update the cache. It also streamlines the internal
queries of the dynamic vertex and fragment shaders such that we only
update the input and output signatures a single time per draw. This
should also facilitate dirty bit implementations for the D3D11 back-
end.

BUG=angleproject:2116

Change-Id: Iccb0501b700bc894f40a8c68d7f297ff0c8f46bd
Reviewed-on: https://chromium-review.googlesource.com/531798Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>