Support parsing const enums.

src/services/syntax/parser.ts

@@ -1098,6 +1098,7 @@ module TypeScript.Parser {
                 case SyntaxKind.StaticKeyword:
                 case SyntaxKind.DeclareKeyword:
                 case SyntaxKind.AsyncKeyword:
+                case SyntaxKind.ConstKeyword:
                     return true;
             }
 
@@ -1117,6 +1118,11 @@ module TypeScript.Parser {
                     }
                 }
 
+                if (token.kind === SyntaxKind.ConstKeyword) {
+                    // In order for 'const' to be a modifier, the next token must be 'enum'.
+                    return nextToken.kind === SyntaxKind.EnumKeyword;
+                }
+
                 var nextTokenKind = nextToken.kind;
                 switch (nextTokenKind) {
                     // public foo'