SW Image Decode Cache Low to Medium Quality for Downscale

cc/tiles/software_image_decode_cache.cc

Index: cc/tiles/software_image_decode_cache.cc
diff --git a/cc/tiles/software_image_decode_cache.cc b/cc/tiles/software_image_decode_cache.cc
index cc1f54fbda0c091f355f0c3a75c338d715879b3e..c41e24024e3d87acb48c2c6046e747fe6e196e79 100644
--- a/cc/tiles/software_image_decode_cache.cc
+++ b/cc/tiles/software_image_decode_cache.cc
@@ -921,14 +921,16 @@ ImageDecodeCacheKey ImageDecodeCacheKey::FromDrawImage(const DrawImage& image) {
   // If we're not going to do a scale, we can use low filter quality. Note that
   // checking if the sizes are the same is better than checking if scale is 1.f,
   // because even non-1 scale can result in the same (rounded) width/height.
-  // If either dimension is a downscale, then use mipmaps (medium filter
-  // quality).
+  // If either dimension is a downscale, and the quality is not None (in which
+  // case we need to preserve the pixelated scale), then use mipmaps (medium
+  // filter quality).
   if (target_size.width() == src_rect.width() &&
       target_size.height() == src_rect.height()) {
     quality = std::min(quality, kLow_SkFilterQuality);
-  } else if (target_size.width() < src_rect.width() ||
-             target_size.height() < src_rect.height()) {
-    quality = std::min(quality, kMedium_SkFilterQuality);
+  } else if (quality != kNone_SkFilterQuality &&
+             (target_size.width() < src_rect.width() ||
+              target_size.height() < src_rect.height())) {
+    quality = kMedium_SkFilterQuality;
   }
 
   // Drop from high to medium if the the matrix we applied wasn't decomposable,