Treat kIncompleteInput as successes in get_images_from_skps

Context:
https://bugs.chromium.org/p/skia/issues/detail?id=5226
and
https://codereview.chromium.org/1844713003/diff/160001/tools/get_images_from_skps.cpp#newcode83

BUG=skia:5226
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1917413003

Review URL: https://codereview.chromium.org/1917413003
diff --git a/tools/get_images_from_skps.cpp b/tools/get_images_from_skps.cpp
index a78c412..11b99c2 100644
--- a/tools/get_images_from_skps.cpp
+++ b/tools/get_images_from_skps.cpp
@@ -82,7 +82,9 @@
             SkBitmap bitmap;
             SkImageInfo info = codec->getInfo().makeColorType(kN32_SkColorType);
             bitmap.allocPixels(info);
-            if (SkCodec::kSuccess != codec->getPixels(info, bitmap.getPixels(),  bitmap.rowBytes()))
+            const SkCodec::Result result = codec->getPixels(
+                info, bitmap.getPixels(),  bitmap.rowBytes());
+            if (SkCodec::kIncompleteInput != result && SkCodec::kSuccess != result)
             {
                 SkDebugf("Decoding failed for %s\n", skpName.c_str());
                 gSkpToUnknownCount[skpName]++;