update allocpixels to know about F16

src/core/SkImageInfo.cpp

Index: src/core/SkImageInfo.cpp
diff --git a/src/core/SkImageInfo.cpp b/src/core/SkImageInfo.cpp
index b90f858562aa8b5f97a495c8ec25afcbec058fe7..6e251a91dc0052bfee42dc19bab4e25b3e21583b 100644
--- a/src/core/SkImageInfo.cpp
+++ b/src/core/SkImageInfo.cpp
@@ -61,6 +61,7 @@ bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
         case kARGB_4444_SkColorType:
         case kRGBA_8888_SkColorType:
         case kBGRA_8888_SkColorType:
+        case kRGBA_F16_SkColorType:
             if (kUnknown_SkAlphaType == alphaType) {
                 return false;
             }