clean up low-hanging swap_rb

There are two remaining swap_rb uses that both look non-trivial to
replace:
   - sampling out of index8 when the color table is bgra
   - table transforms on bgra inputs in SkColorSpaceXform

I don't think it's a big deal to just leave swap_rb around,
just a little sad.

Change-Id: I3d30200cf867cbf37d6f86572b1574d3e22e3490
Reviewed-on: https://skia-review.googlesource.com/21040
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/tests/SkRasterPipelineTest.cpp b/tests/SkRasterPipelineTest.cpp
index 4a951c0..52b4152 100644
--- a/tests/SkRasterPipelineTest.cpp
+++ b/tests/SkRasterPipelineTest.cpp
@@ -216,8 +216,7 @@
     void* ptr = rgba;
 
     SkRasterPipeline_<256> p;
-    p.append(SkRasterPipeline::load_8888,  &ptr);
-    p.append(SkRasterPipeline::swap_rb);
+    p.append(SkRasterPipeline::load_bgra,  &ptr);
     p.append(SkRasterPipeline::store_8888, &ptr);
     p.run(0,0,64);