Comment/test for DocumentMarkerList::MarkersIntersectingRange() with collapsed range

third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.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 DocumentMarkerList_h
 #define DocumentMarkerList_h
 
 #include "core/CoreExport.h"
 #include "core/editing/markers/DocumentMarker.h"
 #include "platform/heap/Handle.h"
@@ skipping 20 matching lines @@
   virtual void Add(DocumentMarker*) = 0;
   virtual void Clear() = 0;
 
   // Returns all markers
   virtual const HeapVector<Member<DocumentMarker>>& GetMarkers() const = 0;
   // Returns the first marker whose interior overlaps with the range
   // [start_offset, end_offset], or null if there is no such marker.
   virtual DocumentMarker* FirstMarkerIntersectingRange(
       unsigned start_offset,
       unsigned end_offset) const = 0;
-  // Returns markers that have non-empty overlap with the range
-  // [start_offset, end_offset]
+  // Returns markers whose interiors have non-empty overlap with the range
+  // [start_offset, end_offset]. Note that the range can be collapsed, in which
+  // case markers containing the offset in their interiors are returned.
   virtual HeapVector<Member<DocumentMarker>> MarkersIntersectingRange(
       unsigned start_offset,
       unsigned end_offset) const = 0;
 
   // Returns true if at least one marker is copied, false otherwise
   virtual bool MoveMarkers(int length, DocumentMarkerList* dst_list) = 0;
 
   // Returns true if at least one marker is removed, false otherwise
   virtual bool RemoveMarkers(unsigned start_offset, int length) = 0;
 
   // Returns true if at least one marker is shifted or removed, false otherwise
   virtual bool ShiftMarkers(unsigned offset,
                             unsigned old_length,
                             unsigned new_length) = 0;
 
   DEFINE_INLINE_VIRTUAL_TRACE() {}
 
  protected:
   DocumentMarkerList();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DocumentMarkerList);
 };
 
 }  // namespace blink
 
 #endif  // DocumentMarkerList_h