Add medium image quality to software predecode.

cc/tiles/software_image_decode_controller.h

 // Copyright 2016 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.
 
 #ifndef CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 #define CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_
 
 #include <stdint.h>
 
 #include <unordered_map>
@@ skipping 166 matching lines @@
   // Get the decoded draw image for the given key and draw_image. Note that this
   // function has to be called with no lock acquired, since it will acquire its
   // own locks and might call DecodeImageInternal above. Also note that this
   // function will use the provided key, even if
   // ImageKey::FromDrawImage(draw_image) would return a different key.
   // Note that when used internally, we still require that
   // DrawWithImageFinished() is called afterwards.
   DecodedDrawImage GetDecodedImageForDrawInternal(const ImageKey& key,
                                                   const DrawImage& draw_image);
 
+  struct DecodedImageResult {
+    DecodedImageResult(SkPixmap decoded_pixmap,
+                       DrawImage original_size_draw_image,
+                       DecodedDrawImage decoded_draw_image);
+
+    SkPixmap decoded_pixmap_;
+    DrawImage original_size_draw_image_;
+    DecodedDrawImage decoded_draw_image_;
+  };
+
+  scoped_ptr<DecodedImage> DecodeImageMediumQuality(const ImageKey& key,
+                                                    const SkImage& image);
+  scoped_ptr<DecodedImage> DecodeImageHighQuality(const ImageKey& key,
+                                                  const SkImage& image);
+
+  scoped_ptr<DecodedImage> AttemptToUseOriginalImage(const ImageKey& key,
+                                                     const SkImage& image);
+
+  DecodedImageResult DecodeImageOrUseCache(const ImageKey& key,
+                                           const SkImage& image);
+
+  scoped_ptr<DecodedImage> ScaleImage(
+      const ImageKey& key,
+      const DecodedImageResult& decoded_image_result);
+
   void SanityCheckState(int line, bool lock_acquired);
   void RefImage(const ImageKey& key);
   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);
-
   std::unordered_map<ImageKey, scoped_refptr<ImageDecodeTask>, ImageKeyHash>
       pending_image_tasks_;
 
   // The members below this comment can only be accessed if the lock is held to
   // ensure that they are safe to access on multiple threads.
   base::Lock lock_;
 
   using ImageMRUCache =
       base::HashingMRUCache<ImageKey, scoped_ptr<DecodedImage>, ImageKeyHash>;
 
@@ skipping 12 matching lines @@
   // 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_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_SOFTWARE_IMAGE_DECODE_CONTROLLER_H_