addMarker() optimizations.

Source/core/dom/DocumentMarker.h

Index: Source/core/dom/DocumentMarker.h
diff --git a/Source/core/dom/DocumentMarker.h b/Source/core/dom/DocumentMarker.h
index b6072b9701c76607f4cd735443d80bbe8d2538b9..cbebc4fc13f60cfa6483b1ab3fb1f88ec1d0a66f 100644
--- a/Source/core/dom/DocumentMarker.h
+++ b/Source/core/dom/DocumentMarker.h
@@ -38,10 +38,17 @@ class DocumentMarkerDetails;
 // for all types other than type TextMatch.
 class DocumentMarker {
 public:
+    enum MarkerTypeIndex {
+        SpellingMarkerIndex = 0,
+        GramarMarkerIndex,
+        TextMatchMarkerIndex,
+        MarkerTypeIndexesCount
+    };
+
     enum MarkerType {
-        Spelling = 1 << 0,
-        Grammar = 1 << 1,
-        TextMatch = 1 << 2
+        Spelling = 1 << SpellingMarkerIndex,
+        Grammar = 1 << GramarMarkerIndex,
+        TextMatch = 1 << TextMatchMarkerIndex
     };
 
     class MarkerTypes {