Add simple bit_cast unittests

base/bit_cast_unittest.cc

+// Copyright (c) 2016 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/bit_cast.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace {
+
+TEST(BitCastTest, FloatIntFloat) {
+  float f = 3.1415926f;
+  int i = bit_cast<int32_t>(f);
+  float f2 = bit_cast<float>(i);
+  EXPECT_EQ(f, f2);
+}
+
+struct A {
+  int x;
+};
+
+TEST(BitCastTest, StructureInt) {
+  A a = { 1 };
+  int b = bit_cast<int>(a);
+  EXPECT_EQ(1, b);
+}
+
+
+}  // namespace
+}  // namespace base