Fix matrix uniform assertion when matrix is unused

[bsalomon, 2012-07-20 14:12:52]

The boilerplate texture-coord generation code inserts a uniform matrix which is
multiplied by the positions to generate texture coords. The color filter LUT
effect ignores the texture coords. Thus, the compiler can optimize out the
matrix. We have an assertion that if a matrix is inserted it ought to have a
valid uniform location. We need to stop emitting this boiler plate code and move
it into a helper for custom effects that want a matrix. The temporary workaround
is to ensure the matrix is identity so that we don't emit it.

[TomH, 2012-07-20 14:13:54]

CL contents don't match description.
Nor do the CL contents make sense.
Misupload?

[TomH, 2012-07-20 14:21:40]

NM, I'm easily confused.
LGTM

[bsalomon, 2012-07-20 16:00:17]

The first fix didn't work because we may later modify the matrix (to draw in
device coords).

The new fix disables the assertion.

[TomH, 2012-07-20 16:15:47]

Even LGTMier.

[twiz1, 2012-07-20 16:19:16]

On 2012/07/20 16:15:47, TomH wrote:
> Even LGTMier.

LGTM, assuming that the commented out code is removed when we refactor to omit
generating texture coord matrices for custom stages with no tex coords.

[bsalomon, 2012-07-20 17:49:37]

Closed with r4693.