Add display-resolution caching to GPU IDC

cc/tiles/mipmap_util.h

Index: cc/tiles/mipmap_util.h
diff --git a/cc/tiles/mipmap_util.h b/cc/tiles/mipmap_util.h
index 800246a7585912250597ded82689f7bebd830a06..521500ef1dee5a62a371da891641dddf98110e96 100644
--- a/cc/tiles/mipmap_util.h
+++ b/cc/tiles/mipmap_util.h
@@ -27,6 +27,11 @@ class CC_EXPORT MipMapUtil {
   static SkSize GetScaleAdjustmentForLevel(const gfx::Size& src_size,
                                            int mip_level);
 
+  // Determine the size of the given |mip_level|. Returns (-1, -1) if
+  // |src_size| is invalid (width/height <= 0) or if mip-level is invalid (==
+  // -1).
+  static gfx::Size GetSizeForLevel(const gfx::Size& src_size, int mip_level);
+
   // Determines the scale factor for the smallest mip level that is larger than
   // |target_size|. Returns (-1, -1) if |src_size| or |target_size| is invalid
   // (width/height <= 0).