experiment: float color components

include/core/SkShader.h

Index: include/core/SkShader.h
diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 60ef280d5ec37f8038fdec42b8820b5c3530bda5..bf6d6ddb42fd59c148a25b4991aa0b911077c368 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -81,6 +81,7 @@ public:
             shadeSpan().
          */
         kConstInY32_Flag = 1 << 1,
+        kSupports4f_Flag = 1 << 2,
     };
 
     /**
@@ -127,6 +128,8 @@ public:
          */
         virtual void shadeSpan(int x, int y, SkPMColor[], int count) = 0;
 
+        virtual void shadeSpan4f(int x, int y, SkPM4f[], int count);
+
         /**
          * The const void* ctx is only const because all the implementations are const.
          * This can be changed to non-const if a new shade proc needs to change the ctx.