Fix highcontrastfilter on ANGLE D3D9

On NVIDIA and Intel GPUs, running the angle_d3d9_es2 config, we were
getting the wrong result from the HSL conversion. From debugging the
shader, it seems that max(x, y) is not necessarily equal to either x
or y. Tried several ways to fix it, but the only reasonably one that
worked was to alter our conditionals. This is slower, but the filter
is already doing a large amount of work.

Bug: skia:7273
Change-Id: I9724285a0d5834cf98189df9efbdc02b5e1de4a7
Reviewed-on: https://skia-review.googlesource.com/68213
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed