cc: Keep PaintImage in DrawImage.

cc/paint/paint_image.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_PAINT_IMAGE_H_
 #define CC_PAINT_PAINT_IMAGE_H_
 
 #include "base/atomic_sequence_num.h"
 #include "base/logging.h"
 #include "cc/paint/paint_export.h"
@@ skipping 24 matching lines @@
                       sk_sp<SkImage> sk_image,
                       AnimationType animation_type = AnimationType::STATIC,
                       CompletionState completion_state = CompletionState::DONE);
   PaintImage(const PaintImage& other);
   PaintImage(PaintImage&& other);
   ~PaintImage();
 
   PaintImage& operator=(const PaintImage& other);
   PaintImage& operator=(PaintImage&& other);
 
-  bool operator==(const PaintImage& other);
+  bool operator==(const PaintImage& other) const;
   explicit operator bool() const { return sk_image_; }
 
   Id stable_id() const { return id_; }
   const sk_sp<SkImage>& sk_image() const { return sk_image_; }
   AnimationType animation_type() const { return animation_type_; }
   CompletionState completion_state() const { return completion_state_; }
 
  private:
   static base::AtomicSequenceNumber s_next_id_;
 
   Id id_;
   sk_sp<SkImage> sk_image_;
   AnimationType animation_type_ = AnimationType::UNKNOWN;
   CompletionState completion_state_ = CompletionState::UNKNOWN;
 };
 
 }  // namespace cc
 
 #endif  // CC_PAINT_PAINT_IMAGE_H_