[DMC #1.9] Move DocumentMarkerListEditor to its own .h/.cpp files

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

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 249 matching lines @@
   return false;
 }
 
 Color DocumentMarker::BackgroundColor() const {
   if (TextCompositionMarkerDetails* details =
           ToTextCompositionMarkerDetails(details_.Get()))
     return details->BackgroundColor();
   return Color::kTransparent;
 }
 
+bool DocumentMarker::EndsBefore(size_t start_offset,
+                                const DocumentMarker* marker) {
+  return start_offset < marker->EndOffset();
+}
+
 DEFINE_TRACE(DocumentMarker) {
   visitor->Trace(details_);
 }
 
 }  // namespace blink