Remove SkEncodedInfo kUnknown_Color and kUnknown_Alpha from public API

src/codec/SkJpegDecoderMgr.h

Index: src/codec/SkJpegDecoderMgr.h
diff --git a/src/codec/SkJpegDecoderMgr.h b/src/codec/SkJpegDecoderMgr.h
index a5078bb2d3085a09134e2ac7c5221ba8cf9023dd..7bc422d4ff0bb67ee9b1e19b1caddb1f42acc5fc 100644
--- a/src/codec/SkJpegDecoderMgr.h
+++ b/src/codec/SkJpegDecoderMgr.h
@@ -43,10 +43,10 @@ public:
     void  init();
 
     /*
-     * Returns the encoded color type of the jpeg, or kUnknown if the
-     * color type can't be determined
+     * Returns true if it successfully sets outColor to the encoded color,
+     * and false otherwise.
      */
-    SkEncodedInfo::Color getEncodedColor();
+    bool getEncodedColor(SkEncodedInfo::Color* outColor);
 
     /*
      * Free memory used by the decode manager