SW Image Decode Cache Low to Medium Quality for Downscale

cc/tiles/software_image_decode_cache.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/tiles/software_image_decode_cache.h"
 
 #include <inttypes.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 903 matching lines @@
   gfx::Size target_size(
       SkScalarRoundToInt(std::abs(src_rect.width() * scale.width())),
       SkScalarRoundToInt(std::abs(src_rect.height() * scale.height())));
 
   // Start with the quality that was requested.
   SkFilterQuality quality = image.filter_quality();
 
   // 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,
   // or if the scaled image will be too large.
   if (quality == kHigh_SkFilterQuality) {
     if (!image.matrix_is_decomposable()) {
       quality = kMedium_SkFilterQuality;
     } else {
       base::CheckedNumeric<size_t> size = 4u;
       size *= target_size.width();
@@ skipping 237 matching lines @@
     }
   }
 }
 
 void SoftwareImageDecodeCache::OnPurgeMemory() {
   base::AutoLock lock(lock_);
   ReduceCacheUsageUntilWithinLimit(0);
 }
 
 }  // namespace cc