Address MSAN bug in SkAnimatedImage::decodeNextFrame

Bug: oss-fuzz:6284
Change-Id: I77537d6624e7d03fbbfe96046300a9dd7d609064
Reviewed-on: https://skia-review.googlesource.com/106930
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>

src/android/SkAnimatedImage.cpp

@@ -176,6 +176,7 @@ int SkAnimatedImage::decodeNextFrame() {
             // Static image. This is okay.
             frameInfo.fRequiredFrame = SkCodec::kNone;
             frameInfo.fAlphaType = fCodec->getInfo().alphaType();
+            frameInfo.fDisposalMethod = SkCodecAnimation::DisposalMethod::kKeep;
             // These fields won't be read.
             frameInfo.fDuration = INT_MAX;
             frameInfo.fFullyReceived = true;