Add medium image quality to software predecode.

cc/tiles/software_image_decode_controller.h

Index: cc/tiles/software_image_decode_controller.h
diff --git a/cc/tiles/software_image_decode_controller.h b/cc/tiles/software_image_decode_controller.h
index 01a73e6a7e439aabfa75be0dd4d90d7ff222164e..14632aad610572e547c5e60294eedd08af152a9b 100644
--- a/cc/tiles/software_image_decode_controller.h
+++ b/cc/tiles/software_image_decode_controller.h
@@ -231,13 +231,6 @@ class CC_EXPORT SoftwareImageDecodeController
   void RefAtRasterImage(const ImageKey& key);
   void UnrefAtRasterImage(const ImageKey& key);
 
-  // These functions indicate whether the images can be handled and cached by
-  // ImageDecodeController or whether they will fall through to Skia (with
-  // exception of possibly prerolling them). Over time these should return
-  // "false" in less cases, as the ImageDecodeController should start handling
-  // more of them.
-  bool CanHandleImage(const ImageKey& key);
-
   // Helper function which dumps all images in a specific ImageMRUCache.
   void DumpImageMemoryForCache(const ImageMRUCache& cache,
                                const char* cache_name,
@@ -261,11 +254,6 @@ class CC_EXPORT SoftwareImageDecodeController
 
   MemoryBudget locked_images_budget_;
 
-  // Note that this is used for cases where the only thing we do is preroll the
-  // image the first time we see it. This mimics the previous behavior and
-  // should over time change as the compositor starts to handle more cases.
-  std::unordered_set<uint32_t> prerolled_images_;
-
   ResourceFormat format_;
 
   // Used to uniquely identify DecodedImages for memory traces.