[DMC #4] Add CompositionMarkerListImpl

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

Index: third_party/WebKit/Source/core/editing/markers/CompositionMarkerListImpl.h
diff --git a/third_party/WebKit/Source/core/editing/markers/CompositionMarkerListImpl.h b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerListImpl.h
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index 0000000000000000000000000000000000000000..b1b1c482b5e847b450e5c5d46291729577d97981
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+++ b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerListImpl.h
@@ -0,0 +1,48 @@
+// 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 CompositionMarkerListImpl_h
+#define CompositionMarkerListImpl_h
+
+#include "core/editing/markers/DocumentMarkerList.h"
+
+namespace blink {
+
+// Implementation of DocumentMarkerList for Composition markers.
+// Composition markers are always inserted in order, aside from some potential
+// oddball cases (e.g. splitting the marker list into two nodes, then undoing
+// the split). This means we can keep the list in sorted order to do some
+// operations more efficiently, while still being able to do inserts in O(1)
+// time at the end of the list.
+class CORE_EXPORT CompositionMarkerListImpl final : public DocumentMarkerList {
+ public:
+  CompositionMarkerListImpl() = default;
+
+  // DocumentMarkerList implementations
+  bool IsEmpty() const final;
+
+  void Add(DocumentMarker*) final;
+  void Clear() final;
+
+  const HeapVector<Member<RenderedDocumentMarker>>& GetMarkers() const final;
+
+  bool MoveMarkers(int length, DocumentMarkerList* dst_list) final;
+  bool RemoveMarkers(unsigned start_offset, int length) final;
+  bool RemoveMarkersUnderWords(const String& node_text,
+                               const Vector<String>& words) final;
+  bool ShiftMarkers(unsigned offset,
+                    unsigned old_length,
+                    unsigned new_length) final;
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  HeapVector<Member<RenderedDocumentMarker>> markers_;
+
+  DISALLOW_COPY_AND_ASSIGN(CompositionMarkerListImpl);
+};
+
+}  // namespace blink
+
+#endif  // CompositionMarkerListImpl_h