[DMC #5.6] Add type cast for SpellCheckMarkerListImpl

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

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.h
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.h b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.h
index 0ec98740b7a903df0f465477a0d413361b4e3cf6..4ec0eec6e76d5cd321775f9a7dba92cf94193364 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.h
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarkerList.h
@@ -6,11 +6,11 @@
 #define DocumentMarkerList_h
 
 #include "core/CoreExport.h"
+#include "core/editing/markers/DocumentMarker.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
-class DocumentMarker;
 class RenderedDocumentMarker;
 
 // This is an interface implemented by classes that DocumentMarkerController
@@ -23,6 +23,9 @@ class CORE_EXPORT DocumentMarkerList
  public:
   virtual ~DocumentMarkerList();
 
+  // Returns the single marker type supported by the list implementation.
+  virtual DocumentMarker::MarkerType MarkerType() const = 0;
+
   virtual bool IsEmpty() const = 0;
 
   virtual void Add(DocumentMarker*) = 0;