funnel all constant colors through append_constant_color()

My next step is to change the uniform_color context to

    struct {
       float r,g,b,a;
       uint32_t rgba;
    };

so that it's trivial to load in both float and 8-bit pipelines.

Change-Id: If9bdde353ced3bf9eb0c63204b4770ed614ad16b
Reviewed-on: https://skia-review.googlesource.com/30481
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/bench/SkRasterPipelineBench.cpp b/bench/SkRasterPipelineBench.cpp
index 0df8086..818ab2b 100644
--- a/bench/SkRasterPipelineBench.cpp
+++ b/bench/SkRasterPipelineBench.cpp
@@ -123,8 +123,9 @@
 
         SkColorSpaceTransferFn from_2dot2 = gamma(  2.2f),
                                  to_2dot2 = gamma(1/2.2f);
-        SkRasterPipeline_<256> p;
-        p.append(SkRasterPipeline::uniform_color, &c);
+        SkSTArenaAlloc<256> alloc;
+        SkRasterPipeline p(&alloc);
+        p.append_constant_color(&alloc, c);
         p.append(SkRasterPipeline::parametric_r, &from_2dot2);
         p.append(SkRasterPipeline::parametric_g, &from_2dot2);
         p.append(SkRasterPipeline::parametric_b, &from_2dot2);