[DMC #5.6] Add type cast for SpellCheckMarkerListImpl

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

Index: third_party/WebKit/Source/core/editing/markers/GrammarMarkerListImpl.h
diff --git a/third_party/WebKit/Source/core/editing/markers/GrammarMarkerListImpl.h b/third_party/WebKit/Source/core/editing/markers/GrammarMarkerListImpl.h
new file mode 100644
index 0000000000000000000000000000000000000000..5acd5a83119ecccccd8fa71d43a38bb96fe7dd57
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/markers/GrammarMarkerListImpl.h
@@ -0,0 +1,24 @@
+// 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 GrammarMarkerListImpl_h
+#define GrammarMarkerListImpl_h
+
+#include "core/editing/markers/SpellCheckMarkerListImpl.h"
+
+namespace blink {
+
+// This is the DocumentMarkerList implementation used to store Grammar markers.
+class GrammarMarkerListImpl final : public SpellCheckMarkerListImpl {
+ public:
+  GrammarMarkerListImpl() = default;
+
+  DocumentMarker::MarkerType MarkerType() const final;
+
+  DISALLOW_COPY_AND_ASSIGN(GrammarMarkerListImpl);
+};
+
+}  // namespace blink
+
+#endif  // GrammarMarkerListImpl_h