Re-re-relanding after clang warning fix.

Re-re-landing with fix to setting qualifiers on generated nodes. The
previous version failed when a uniform was indexed, because it would
set the uniform qualifier on some of the generated nodes and that
interfered with the operation of UniformsHLSL.

Re-landing after fixing D3D9 specific issues.

HLSL doesn't support dynamic indexing of matrices and vectors, so replace
that with helper functions that unroll dynamic indexing into switch/case
and static indexing.

Both the indexed vector/matrix expression and the index may have side
effects, and these will be evaluated correctly. If necessary, index
expressions that have side effects will be written to a temporary
variable that will replace the index.

Besides dEQP tests, this change is tested by a WebGL 2 conformance test.

In the case that a dynamic index is out-of-range, the base ESSL 3.00 spec
allows undefined behavior. KHR_robust_buffer_access_behavior adds the
requirement that program termination should not occur and that
out-of-range reads must return either a value from the active program's
memory or zero, and out-of-range writes should only affect the active
program's memory or do nothing. This patch clamps out-of-range indices so
that either the first or last item of the matrix/vector is accessed.

The code is not transformed in case the it fits within the limited subset
of ESSL 1.00 given in Appendix A of the spec. If the code isn't within
the restricted subset, even ESSL 1.00 shaders may require this
workaround.

BUG=angleproject:1116
TEST=dEQP-GLES3.functional.shaders.indexing.* (all pass after change)
     WebGL 2 conformance tests (glsl3/vector-dynamic-indexing.html)

Change-Id: I9f6d7c7ecda8ac4dc3c30b39e15a9a0b5381c5a8
Reviewed-on: https://chromium-review.googlesource.com/310010Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>