Allow whitespace and \ before the first newline of multiline string.

tests/compiler/dart2js/string_escapes_test.dart

Index: tests/compiler/dart2js/string_escapes_test.dart
diff --git a/tests/compiler/dart2js/string_escapes_test.dart b/tests/compiler/dart2js/string_escapes_test.dart
index f439689b8dbe6617d03b3225006130ce4ca089f2..1c62a250f1161f15094e089ec4dd2e44123917e1 100644
--- a/tests/compiler/dart2js/string_escapes_test.dart
+++ b/tests/compiler/dart2js/string_escapes_test.dart
@@ -17,13 +17,53 @@ Future<String> compileExpression(String expression) {
 main() {
   asyncTest(() => Future.wait([
     compileExpression("''' \n\r\u2028\u2029'''").then((String generated) {
-      Expect.isTrue(generated.contains(r"\n\r\u2028\u2029"));
+      Expect.isTrue(generated.contains(r'"\r\u2028\u2029"') ||
+                    generated.contains(r"'\r\u2028\u2029'"));
     }),
     compileExpression("r''' \n\r\u2028\u2029'''").then((String generated) {
-      Expect.isTrue(generated.contains(r"\n\r\u2028\u2029"));
+      Expect.isTrue(generated.contains(r'"\r\u2028\u2029"') ||
+                    generated.contains(r"'\r\u2028\u2029'"));
+    }),
+    compileExpression("r''' \r\n\u2028\u2029'''").then((String generated) {
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
+    }),
+    compileExpression("r''' \r\u2028\u2029'''").then((String generated) {
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
+    }),
+    compileExpression("r''' \n\u2028\u2029'''").then((String generated) {
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
+    }),
+    compileExpression("r'''\t\t      \t\t  \t\t  \t \t \n\r\u2028\u2029'''")
+        .then((String generated) {
+      Expect.isTrue(generated.contains(r'"\r\u2028\u2029"') ||
+                    generated.contains(r"'\r\u2028\u2029'"));
+    }),
+    compileExpression("r'''\\\t\\\t \\   \\  \t\\\t  \t \\\n\r\u2028\u2029'''")
+        .then((String generated) {
+      Expect.isTrue(generated.contains(r'"\r\u2028\u2029"') ||
+                    generated.contains(r"'\r\u2028\u2029'"));
+    }),
+    compileExpression("r'''\t\t      \t\t  \t\t  \t \t \\\n\r\u2028\u2029'''")
+        .then((String generated) {
+      Expect.isTrue(generated.contains(r'"\r\u2028\u2029"') ||
+                    generated.contains(r"'\r\u2028\u2029'"));
+    }),
+    compileExpression("r'''\\\t\\\t \\   \\  \t\\\t   \\\r\n\u2028\u2029'''")
+        .then((String generated) {
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
+    }),
+    compileExpression("r'''\\\t\\\t \\   \\  \t\\\t   \\\r\u2028\u2029'''")
+        .then((String generated) {
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
     }),
     compileExpression("'\u2028\u2029'").then((String generated) {
-      Expect.isTrue(generated.contains(r"\u2028\u2029"));
+      Expect.isTrue(generated.contains(r'"\u2028\u2029"') ||
+                    generated.contains(r"'\u2028\u2029'"));
     }),
   ]));
 }