Add support to dart2js for option --enable-asserts.

tests/corelib/list_removeat_test.dart

Index: tests/corelib/list_removeat_test.dart
diff --git a/tests/corelib/list_removeat_test.dart b/tests/corelib/list_removeat_test.dart
index 758e9204dffd2f0721cfd0daa417ad1f89f77636..ca058835de5f3b24f468ff6004ea65113a5d3b67 100644
--- a/tests/corelib/list_removeat_test.dart
+++ b/tests/corelib/list_removeat_test.dart
@@ -20,11 +20,18 @@ class MyList extends ListBase {
   String toString() => "[" + join(", ") + "]";
 }
 
+final bool isCheckedMode = (() {
+  try {
+    var i = 42;
+    String s = i;
+  } on TypeError catch (e) {
+    return true;
+  }
+  return false;
+})();

[sra1, 2017/05/24 01:30:46]

delete

[eernst, 2017/07/07 08:50:29]

Done.

+
 // l1 must be a modifiable list with 5 elements from 0 to 4.
 void testModifiableList(l1) {
-  bool checkedMode = false;
-  assert(checkedMode = true);
-
   // Index must be integer and in range.
   Expect.throws(() {
     l1.removeAt(-1);
@@ -37,10 +44,12 @@ void testModifiableList(l1) {
   }, (e) => e is ArgumentError, "too large");
   Expect.throws(() {
     l1.removeAt("1");
-  }, (e) => (checkedMode ? e is TypeError : e is ArgumentError), "string");
+  }, (e) => (typeAssertionsEnabled ? e is TypeError : e is ArgumentError),
+      "string");
   Expect.throws(() {
     l1.removeAt(1.5);
-  }, (e) => (checkedMode ? e is TypeError : e is ArgumentError), "double");
+  }, (e) => (typeAssertionsEnabled ? e is TypeError : e is ArgumentError),
+      "double");
 
   Expect.equals(2, l1.removeAt(2), "l1-remove2");
   Expect.equals(1, l1[1], "l1-1[1]");