Handle escapes in string literals.

frog/tests/leg/src/BuiltinInterceptorTest.dart

Index: frog/tests/leg/src/BuiltinInterceptorTest.dart
diff --git a/frog/tests/leg/src/BuiltinInterceptorTest.dart b/frog/tests/leg/src/BuiltinInterceptorTest.dart
index 05061e534e10cfbecba744c741e6b2a47d72df37..a5d617cf35a137cdcda32158f2d812f81b604566 100644
--- a/frog/tests/leg/src/BuiltinInterceptorTest.dart
+++ b/frog/tests/leg/src/BuiltinInterceptorTest.dart
@@ -26,17 +26,11 @@ main() {
   String generated = compile(TEST_ONE, 'foo');
   Expect.isTrue(generated.contains("return a.length;"));
 
-  // TODO(ngeoffray): Enable once we support raw strings
-  // and folding of length.
-  Exception exception;
-  try {
-    generated = compile(TEST_TWO, 'foo');
-    Expect.isTrue(generated.contains("return 3;"));
+  // TODO(lrn): Switch these two to isTrue when we support constant folding
+  // of string length.
+  generated = compile(TEST_TWO, 'foo');
+  Expect.isFalse(generated.contains("return 3;"));
 
-    generated = compile(TEST_THREE, 'foo');
-    Expect.isTrue(generated.contains("return 3;"));
-  } catch (var e) {
-    exception = e;
-  }
-  Expect.isTrue(exception != null);
+  generated = compile(TEST_THREE, 'foo');
+  Expect.isFalse(generated.contains("return 3;"));
 }