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 20dc4511f23a95e0a97fc77ef29c396c987fcf17..7276dca6ec26aec4eadac2577581765ab34dacb6 100644
--- a/cc/tiles/software_image_decode_controller.h
+++ b/cc/tiles/software_image_decode_controller.h
@@ -184,18 +184,38 @@ class CC_EXPORT SoftwareImageDecodeController : public ImageDecodeController {
   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> DecodeImageNoneLowQuality(const ImageKey& key,
+                                                     const SkImage& 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_;