[DMC #24] Add SpellingMarker and GrammarMarker (subclasses of DocumentMarker)

third_party/WebKit/Source/core/editing/markers/GrammarMarker.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 GrammarMarker_h
+#define GrammarMarker_h
+
+#include "core/editing/markers/SpellCheckMarker.h"
+
+namespace blink {
+
+// A subclass of DocumentMarker used to store information specific to grammar
+// markers. Spelling and grammar markers are identical except that they mark
+// either spelling or grammar errors, respectively, so nearly all functionality
+// is delegated to a common base class, SpellCheckMarker.
+class CORE_EXPORT GrammarMarker final : public SpellCheckMarker {
+ public:
+  GrammarMarker(unsigned start_offset,
+                unsigned end_offset,
+                const String& description);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(GrammarMarker);
+};
+
+}  // namespace blink
+
+#endif