Made assert a keyword.

lib/compiler/implementation/lib/js_helper.dart

Index: lib/compiler/implementation/lib/js_helper.dart
diff --git a/lib/compiler/implementation/lib/js_helper.dart b/lib/compiler/implementation/lib/js_helper.dart
index 7170d2c1b158cbb4c4aacc801d790602808de2d3..07c28ae63d56f5486f177f63d34a6c33b91959d2 100644
--- a/lib/compiler/implementation/lib/js_helper.dart
+++ b/lib/compiler/implementation/lib/js_helper.dart
@@ -1361,7 +1361,7 @@ class FallThroughErrorImplementation implements FallThroughError {
 /**
  * Helper function for implementing asserts. The compiler treats this specially.
  */
-void assert(condition) {
+void assertHelper(condition) {
   if (condition is Function) condition = condition();
   if (condition is !bool) {
     throw new TypeErrorImplementation(condition, 'bool');