cc: Make PaintCanvas abstract

cc/paint/paint_recorder.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_RECORDER_H_
 #define CC_PAINT_PAINT_RECORDER_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/optional.h"
 #include "cc/paint/paint_canvas.h"
 #include "cc/paint/paint_record.h"
+#include "cc/paint/skia_paint_canvas.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 
 namespace cc {
 
 class CC_PAINT_EXPORT PaintRecorder {
  public:
   PaintRecorder();
   ~PaintRecorder();
 
   ALWAYS_INLINE PaintCanvas* beginRecording(const SkRect& bounds) {
@@ skipping 30 matching lines @@
       const SkRect& cull_rect,
       uint32_t end_flags = 0) {
     sk_sp<SkPicture> picture =
         recorder_.finishRecordingAsPictureWithCull(cull_rect, end_flags);
     canvas_.reset();
     return sk_ref_sp(static_cast<PaintRecord*>(picture.get()));
   }
 
  private:
   SkPictureRecorder recorder_;
-  base::Optional<PaintCanvas> canvas_;
+  base::Optional<SkiaPaintCanvas> canvas_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintRecorder);
 };
 
 }  // namespace cc
 
 #endif  // CC_PAINT_PAINT_RECORDER_H_