This reverts commit 3766a40d.

This CL was causing crashes in UniformHLSL.cpp, where an internal
uniform "base" was attempted to be declared in HLSL. Was crashing
on an external WebGL 3D canvas page (http://www.taccgl.org/?dbg=t).

BUG=546686

Original commit message:

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: I1d4b2e3888e91af7d5eebf743d12778698b6b903
Reviewed-on: https://chromium-review.googlesource.com/308770Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>