Trying to compile user-defined functions that have thousands of
parameters introduces some instability in native compilers, so it is
better to reject shaders with large numbers of function parameters
in ANGLE.

The check is only enabled if the SH_LIMIT_EXPRESSION_COMPLEXITY flag
is turned on. The default limit for the number of parameters is 1024,
but it can also be configured.

BUG=angleproject:1338
TEST=angle_unittests

Change-Id: I5c9b7a4e97e67f36e77f969368336fa8fffba1c3
Reviewed-on: https://chromium-review.googlesource.com/331970Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>