Update handling of multiline strings to specification.

tests/language/multiline_newline_cr.dart

Index: tests/language/multiline_newline_cr.dart
diff --git a/tests/language/multiline_newline_cr.dart b/tests/language/multiline_newline_cr.dart
index f7251594e76307595b63f5ca6522a52c8685bad7..f793f54cfec176b273b46c7fabc17a769013672d 100644
--- a/tests/language/multiline_newline_cr.dart
+++ b/tests/language/multiline_newline_cr.dart
@@ -7,3 +7,7 @@ library multiline_newline_cr;
 const constantMultilineString = """
a
b
""";
 
 var nonConstantMultilineString = """
a
b
""";
+
+const constantRawMultilineString = r"""
\a
\b
""";
+
+var nonConstantRawMultilineString = r"""
\a
\b
""";