Add TextMatchMarkerList in preparation for DocumentMarkerController refactor

third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp
index 622932e6f9a91cbaf42cf0f61952a7d66bb84531..6926df4d0ba075e1dd81af9a73096c091a204de7 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.cpp
@@ -86,13 +86,13 @@ DocumentMarkerList::DidRemoveMarkerOrNot DocumentMarkerList::removeMarkers(
 
     // add either of the resulting slices that are left after removing target
     if (startOffset > marker->startOffset()) {
-      DocumentMarker* newLeft = new DocumentMarker(*marker);
+      DocumentMarker* newLeft = marker->clone();
       newLeft->setEndOffset(startOffset);
       newMarkerList.push_back(newLeft);
     }
 
     if (marker->endOffset() > endOffset) {
-      DocumentMarker* newRight = new DocumentMarker(*marker);
+      DocumentMarker* newRight = marker->clone();
       newRight->setStartOffset(endOffset);
       newMarkerList.push_back(newRight);
     }