send SkPMColor::toPMColor() through Sk4f_toL32()

This doesn't fix that 8888 gradient if we stop clamping,
but it seems like a good idea to land first anyway.

Change-Id: Ie0feda67da5996223db2fe4458f99d57cf13db71
Reviewed-on: https://skia-review.googlesource.com/155782
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/utils/SkPatchUtils.cpp b/src/utils/SkPatchUtils.cpp
index 83495bc..ca92415 100644
--- a/src/utils/SkPatchUtils.cpp
+++ b/src/utils/SkPatchUtils.cpp
@@ -7,6 +7,7 @@
 
 #include "SkPatchUtils.h"
 
+#include "SkArenaAlloc.h"
 #include "SkColorData.h"
 #include "SkColorSpacePriv.h"
 #include "SkGeometry.h"