Implement assert in initializer list in VM.

runtime/lib/errors_patch.dart

Index: runtime/lib/errors_patch.dart
diff --git a/runtime/lib/errors_patch.dart b/runtime/lib/errors_patch.dart
index 89ade45e16c658ffda151d18fe5b6fdeafefc758..77251fecb08b8b081c8399a98dac8b0df31d7c3d 100644
--- a/runtime/lib/errors_patch.dart
+++ b/runtime/lib/errors_patch.dart
@@ -35,6 +35,12 @@ class _AssertionError extends Error implements AssertionError {
     }
   }
 
+  static void _checkConstAssertion(bool condition, int start, int end) {
+    if (!condition) {
+      _throwNew(start, end);
+    }
+  }
+
   String toString() {
     if (_url == null) {
       return _failedAssertion;