Add check that no aggressive & incorrect optimizations is done.

tests/language/mul_recipr_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// Dart test program checking that optimizations are not too aggresive and
+// incorrect:
+// - (a * (1.0 / b))
+//
+// VMOptions=--optimization-counter-threshold=8 --no-use-osr
+
+import "package:expect/expect.dart";
+
+var xx = 23.0;
+
+main() {
+  xx = 1e-6;
+  scaleIt(1e-310);
+  Expect.isTrue(xx.isInfinite);
+  for (int i = 0; i < 10; i++) {
+    xx = 24.0;
+    scaleIt(6.0);
+    Expect.equals(4.0, xx);
+  }
+  xx = 1e-6;
+  scaleIt(1e-310);
+  Expect.isTrue(xx.isInfinite);
+}
+
+scaleIt(double b) {
+  scale(1.0 / b);
+}
+
+scale(a) {
+  xx *= a;
+}