Add type inference for assert statements.

pkg/front_end/testcases/inference/assert.dart.direct.expect

Index: pkg/front_end/testcases/inference/assert.dart.direct.expect
diff --git a/pkg/front_end/testcases/inference/assert.dart.direct.expect b/pkg/front_end/testcases/inference/assert.dart.direct.expect
new file mode 100644
index 0000000000000000000000000000000000000000..e5a1b8f36be33f770afb6cc87ccf0ef411407270
--- /dev/null
+++ b/pkg/front_end/testcases/inference/assert.dart.direct.expect
@@ -0,0 +1,11 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+static method f<T extends core::Object>() → self::f::T
+  return null;
+static method test() → void {
+  assert(self::f<dynamic>());
+  assert(self::f<dynamic>(), self::f<dynamic>());
+}
+static method main() → dynamic {}