Add gm for displaying different variants of 8888 bitmaps and fix a small rejection case for sprite blitters.

BUG=skia:5378
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2036493004

Review-Url: https://codereview.chromium.org/2036493004

1 files changed, 6 insertions, 0 deletions

diff --git a/src/core/SkBlitter_Sprite.cpp b/src/core/SkBlitter_Sprite.cpp
index 2ddc5f4855..dc912b0f65 100644
--- a/src/core/SkBlitter_Sprite.cpp
+++ b/src/core/SkBlitter_Sprite.cpp
@@ -149,6 +149,12 @@ SkBlitter* SkBlitter::ChooseSprite(const SkPixmap& dst, const SkPaint& paint,
     */
     SkASSERT(allocator != nullptr);
 
+    // Defer to the general code if the pixels are unpremultipled. This case is not common,
+    // and this simplifies the code.
+    if (source.alphaType() == kUnpremul_SkAlphaType) {
+        return nullptr;
+    }
+
     SkSpriteBlitter* blitter = nullptr;
 
     if (SkSpriteBlitter_Src_SrcOver::Supports(dst, source, paint)) {