Adjust the alpha type for pixelRefs.

include/core/SkImageInfo.h

Index: include/core/SkImageInfo.h
diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index b955433329579d6907da98a085e8b72759818fdf..890fe5e6b823d4026c0c18b1557c30258b3b750d 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -120,6 +120,15 @@ static inline bool SkColorTypeIsValid(unsigned value) {
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
+ *  Return true if alphaType is supported by colorType. If there is a canonical
+ *  alphaType for this colorType, return it in canonical.
+ */
+bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
+                                  SkAlphaType* canonical = NULL);
+
+///////////////////////////////////////////////////////////////////////////////
+
+/**
  *  Describe an image's dimensions and pixel type.
  */
 struct SkImageInfo {