Remove SkEncodedInfo kUnknown_Color and kUnknown_Alpha from public API

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 0799e813813d719fdcb0ba6561daa689ed3d3bde..7de97b39ab328cee0c58767b8f90df348f64fbdb 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -212,8 +212,8 @@ bool SkJpegCodec::ReadHeader(SkStream* stream, SkCodec** codecOut,
 
     if (codecOut) {
         // Get the encoded color type
-        SkEncodedInfo::Color color = decoderMgr->getEncodedColor();
-        if (SkEncodedInfo::kUnknown_Color == color) {
+        SkEncodedInfo::Color color;
+        if (!decoderMgr->getEncodedColor(&color)) {
             return false;
         }