Add DocumentMarker::clone()

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

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
index dbcfdf2964555be13aa50b7551bf2305f37a6fd8..72840834c21b4c5fbbfb2a55acae527541cec303 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
@@ -134,6 +134,8 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
     SpellCheckClientMarkers() : MarkerTypes(Spelling | Grammar) {}
   };
 
+  virtual DocumentMarker* clone() const;
+
   DocumentMarker(MarkerType,
                  unsigned startOffset,
                  unsigned endOffset,
@@ -145,8 +147,6 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
                  bool thick,
                  Color backgroundColor);
 
-  DocumentMarker(const DocumentMarker&);
-
   MarkerType type() const { return m_type; }
   unsigned startOffset() const { return m_startOffset; }
   unsigned endOffset() const { return m_endOffset; }
@@ -176,6 +176,9 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
 
   DECLARE_TRACE();
 
+ protected:
+  DocumentMarker(const DocumentMarker&);
+
  private:
   MarkerType m_type;
   unsigned m_startOffset;