Support decoding opaque to *premul

If a client requests unpremul or premul from an opaque SkCodec,
support it. The opaque image can be treated as any of them, though
it will be less efficient to draw than if the client had used
opaque.

Change the filling code (i.e. for incomplete images) to base its color on
the source alpha type. Prior to adding the support to decode opaque to
any, it was fine to use either source or dest (which would have yielded
the same result). If the client requests non-opaque, we do not want this
to switch the fill value from black to transparent. This also allows
simplifying the signatures for getFillValue and onGetFillValue.

In CodexTest, expect the same result when decoding opaque to *premul,
and compare to the opaque version.

BUG=skia:4616
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1641273003

Review URL: https://codereview.chromium.org/1641273003

1 files changed, 4 insertions, 2 deletions

diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index d02eeaf101..a719bd154a 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -118,7 +118,7 @@ public:
         kIndex8_Always_DstColorType,
         kGrayscale_Always_DstColorType,
     };
-    CodecSrc(Path, Mode, DstColorType, float);
+    CodecSrc(Path, Mode, DstColorType, SkAlphaType, float);
 
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
@@ -128,6 +128,7 @@ private:
     Path                    fPath;
     Mode                    fMode;
     DstColorType            fDstColorType;
+    SkAlphaType             fDstAlphaType;
     float                   fScale;
 };
 
@@ -140,7 +141,7 @@ public:
         kDivisor_Mode,
     };
 
-    AndroidCodecSrc(Path, Mode, CodecSrc::DstColorType, int sampleSize);
+    AndroidCodecSrc(Path, Mode, CodecSrc::DstColorType, SkAlphaType, int sampleSize);
 
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
@@ -150,6 +151,7 @@ private:
     Path                    fPath;
     Mode                    fMode;
     CodecSrc::DstColorType  fDstColorType;
+    SkAlphaType             fDstAlphaType;
     int                     fSampleSize;
 };