cc: Keep PaintImage in DrawImage.

cc/paint/image_id.h

 // Copyright 2017 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_PAINT_IMAGE_ID_H_
 #define CC_PAINT_IMAGE_ID_H_
 
 #include <stdint.h>
 #include <unordered_set>
 
 #include "base/containers/flat_set.h"
+#include "cc/paint/paint_image.h"
 
 namespace cc {
 
-using ImageId = uint32_t;
-using ImageIdFlatSet = base::flat_set<ImageId>;
+using PaintImageIdFlatSet = base::flat_set<PaintImage::Id>;
+
+// TODO(khushalsagar): These are only used by the hijack canvas since it uses
+// an SkCanvas to replace images. Remove once that moves to PaintOpBuffer.
+using SkImageId = uint32_t;
+using SkImageIdFlatSet = base::flat_set<SkImageId>;
 
 }  // namespace cc
 
 #endif  // CC_PAINT_IMAGE_ID_H_