Add numeric_cast for checked integral narrowing casts

base/safe_numerics_unittest.nc

Index: base/safe_numerics_unittest.nc
diff --git a/base/safe_numerics_unittest.nc b/base/safe_numerics_unittest.nc
new file mode 100644
index 0000000000000000000000000000000000000000..2c59871369a2f6ea10188bba36cdec57f30a22a8
--- /dev/null
+++ b/base/safe_numerics_unittest.nc
@@ -0,0 +1,17 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/safe_numerics.h"
+
+namespace base {
+namespace internal {
+
+void NoFloatingPoint {
+  IsValidNumericCast<float>(0.0);
+  IsValidNumericCast<double>(0.0f);
+  IsValidNumericCast<int>(DBL_MAX);
+}
+
+}  // namespace internal
+}  // namespace base