cc: Keep PaintImage in DrawImage.

cc/paint/paint_image.cc

Index: cc/paint/paint_image.cc
diff --git a/cc/paint/paint_image.cc b/cc/paint/paint_image.cc
index 0a19352355c2c7ac979d6cf59ba9c249cab15f02..fc22a57da961b87aca0be993752b9e8ef7ee203c 100644
--- a/cc/paint/paint_image.cc
+++ b/cc/paint/paint_image.cc
@@ -24,7 +24,7 @@ PaintImage::~PaintImage() = default;
 PaintImage& PaintImage::operator=(const PaintImage& other) = default;
 PaintImage& PaintImage::operator=(PaintImage&& other) = default;
 
-bool PaintImage::operator==(const PaintImage& other) {
+bool PaintImage::operator==(const PaintImage& other) const {
   return id_ == other.id_ && sk_image_ == other.sk_image_ &&
          animation_type_ == other.animation_type_ &&
          completion_state_ == other.completion_state_;