Change assert implementation to not depend on a top-level function called 'assert'.

lib/compiler/implementation/universe.dart

Index: lib/compiler/implementation/universe.dart
diff --git a/lib/compiler/implementation/universe.dart b/lib/compiler/implementation/universe.dart
index ea75d9a76cf98b2a634ebb11466180f9ed67f3b9..588ff8bfd6784ff612b32fed953d25a1f49eafd7 100644
--- a/lib/compiler/implementation/universe.dart
+++ b/lib/compiler/implementation/universe.dart
@@ -171,6 +171,14 @@ class Selector implements Hashable {
   bool isUnaryOperator() => isOperator() && argumentCount == 0;
   bool isBinaryOperator() => isOperator() && argumentCount == 1;
 
+  /** Check whether this is a call to 'assert' with one positional parameter. */
+  bool isAssertSyntax() {
+    return (isCall() &&
+            name.stringValue === "assert" &&
+            argumentCount == 1 &&
+            namedArgumentCount == 0);
+  }
+
   int hashCode() => argumentCount + 1000 * namedArguments.length;
   int get namedArgumentCount => namedArguments.length;
   int get positionalArgumentCount => argumentCount - namedArgumentCount;