Add TextMatchMarkerList in preparation for DocumentMarkerController refactor

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 491ea4e401f73541d6721743efb620fe2e5ed623..0ba0763f4dce29696daf4de502f306a3561baa7f 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;

[Xiaocheng, 2017/03/29 23:20:57]

The introduction of clone() seems pretty light weight and orthogonal to
everything else.

Let's split it into another patch, which seems landable before all other
patches.

Let's also use it in copyMarkers() so that we can get rid of the multiple
reference issue.

+
   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; }
@@ -186,6 +186,9 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
 
   DECLARE_TRACE();
 
+ protected:
+  DocumentMarker(const DocumentMarker&);
+
  private:
   MarkerType m_type;
   unsigned m_startOffset;