bitmapshader with A8 bitmap should be colorized by the paint's color

include/core/SkPaint.h

Index: include/core/SkPaint.h
diff --git a/include/core/SkPaint.h b/include/core/SkPaint.h
index 2b30a7cda5d5950084804280c03217a5103ae20a..5e0186375a4a409f6b12d2382243ed4318a4b49b 100644
--- a/include/core/SkPaint.h
+++ b/include/core/SkPaint.h
@@ -514,6 +514,10 @@ public:
      *  once (e.g. bitmap tiling or gradient) and then change its transparency
      *  w/o having to modify the original shader... only the paint's alpha needs
      *  to be modified.
+     *
+     *  The only exception is that the shader's bitmap is kA8_Config. In that case,
+     *  the paint's color is used, and modulated by the shader's alpha.
+     *
      *  <p />
      *  Pass NULL to clear any previous shader.
      *  As a convenience, the parameter passed is also returned.