Add DocumentMarkerList implementation classes

third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.h

Index: third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.h
diff --git a/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.h b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.h
new file mode 100644
index 0000000000000000000000000000000000000000..9bb15f57d8e23767dda966851ba5ec9a83b8bed9
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.h
@@ -0,0 +1,43 @@
+// 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 CompositionMarkerList_h
+#define CompositionMarkerList_h
+
+#include "core/editing/markers/DocumentMarkerList.h"
+
+namespace blink {
+
+class CORE_EXPORT CompositionMarkerList final : public DocumentMarkerList {
+ public:
+  CompositionMarkerList();
+
+  bool Empty() const final;
+
+  void Add(DocumentMarker*) final;
+  void Clear() final;
+
+  void AppendMarkersToInputList(DocumentMarkerVector* list) const;
+
+  bool MoveMarkers(int length, DocumentMarkerList* dst_list) final;
+
+  bool RemoveMarkers(unsigned start_offset, int length);
+
+  bool ShiftMarkers(unsigned offset,
+                    unsigned old_length,
+                    unsigned new_length) final;
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  HeapVector<Member<DocumentMarker>> markers_;
+
+  DISALLOW_COPY_AND_ASSIGN(CompositionMarkerList);
+};
+
+DEFINE_TYPE_CASTS(CompositionMarkerList, DocumentMarkerList, list, true, true);
+
+}  // namespace blink
+
+#endif  // CompositionMarkerList_h