Add DocumentMarker::clone()

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

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarkerController.cpp
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerController.cpp b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerController.cpp
index 34506d1809171ca1ef41fdc04d995e252f4aa773..88a086d66a04c0dfddc71b9e67c2b84303420bb7 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerController.cpp
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerController.cpp
@@ -381,7 +381,7 @@ void DocumentMarkerController::removeMarkers(
     MarkerList::iterator startPos =
         std::upper_bound(list->begin(), list->end(), startOffset, endsBefore);
     for (MarkerList::iterator i = startPos; i != list->end();) {
-      DocumentMarker marker(*i->get());
+      const DocumentMarker& marker(*i->get());
 
       // markers are returned in order, so stop if we are now past the specified
       // range
@@ -401,18 +401,18 @@ void DocumentMarkerController::removeMarkers(
 
       // add either of the resulting slices that are left after removing target
       if (startOffset > marker.startOffset()) {
-        DocumentMarker newLeft = marker;
-        newLeft.setEndOffset(startOffset);
+        DocumentMarker* newLeft =
+            marker.cloneWithNewOffsets(marker.startOffset(), startOffset);
         size_t insertIndex = i - list->begin();
-        list->insert(insertIndex, RenderedDocumentMarker::create(newLeft));
+        list->insert(insertIndex, RenderedDocumentMarker::create(*newLeft));
         // Move to the marker after the inserted one.
         i = list->begin() + insertIndex + 1;
       }
       if (marker.endOffset() > endOffset) {
-        DocumentMarker newRight = marker;
-        newRight.setStartOffset(endOffset);
+        DocumentMarker* newRight =
+            marker.cloneWithNewOffsets(endOffset, marker.endOffset());
         size_t insertIndex = i - list->begin();
-        list->insert(insertIndex, RenderedDocumentMarker::create(newRight));
+        list->insert(insertIndex, RenderedDocumentMarker::create(*newRight));
         // Move to the marker after the inserted one.
         i = list->begin() + insertIndex + 1;
       }