NormalizeWhitespace does not automatically insert a newline after documentation

Version Used: Mircrosoft.CodeAnalysis.Common : 4.0.30319

Steps to Reproduce:

1. Emit a method using the following declaration:

MethodDeclaration(
	PredefinedType(
		Token(SyntaxKind.IntKeyword)),
	Identifier("Method"))
.WithAttributeLists(
	SingletonList(
		AttributeList(
				SingletonSeparatedList<AttributeSyntax>(
					Attribute(
						IdentifierName("Pure"))))
			.WithOpenBracketToken(
				Token(
					TriviaList(
						Trivia(
							DocumentationCommentTrivia(
								SyntaxKind.SingleLineDocumentationCommentTrivia,
								SingletonList<XmlNodeSyntax>(
									XmlText()
										.WithTextTokens(
											TokenList(
												new []{
													XmlTextLiteral(
														TriviaList(
															DocumentationCommentExterior("///")),
														" Some cool documentation",
														" Some cool documentation",
														TriviaList())})))))),
					SyntaxKind.OpenBracketToken,
					TriviaList()))))
.WithModifiers(
	TokenList(
		Token(SyntaxKind.PublicKeyword)))
.WithBody(
	Block(
		SingletonList<StatementSyntax>(
			ReturnStatement(
				LiteralExpression(
					SyntaxKind.NumericLiteralExpression,
					Literal(1))))))
.NormalizeWhitespace());

Expected Behavior: Should automatically output a new line after the documentation

/// Some cool documentation
[Pure]
public int Method()
{
    return 1;
}

Actual Behavior: Does not output a new line after the documentation

/// Some cool documentation[Pure]
public int Method()
{
    return 1;
}

Manually adding a XmlTextNewLine token at the end of the documentation resolves the issue, not sure if this is the intended behavior.