Add RandomNumberGenerator adapter to base/rand_util.h

base/rand_util_unittest.cc

 // Copyright (c) 2008 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/rand_util.h"
 
 #include <limits>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
 const int kIntMin = std::numeric_limits<int>::min();
 const int kIntMax = std::numeric_limits<int>::max();
 
 }  // namespace
 
 TEST(RandUtilTest, SameMinAndMax) {
   EXPECT_EQ(base::RandInt(0, 0), 0);
   EXPECT_EQ(base::RandInt(kIntMin, kIntMin), kIntMin);
   EXPECT_EQ(base::RandInt(kIntMax, kIntMax), kIntMax);
 }
 
 TEST(RandUtilTest, RandDouble) {
  // Force 64-bit precision, making sure we're not in a 80-bit FPU register.
  volatile double number = base::RandDouble();
  EXPECT_GT(1.0, number);
  EXPECT_LE(0.0, number);
 }
+
+// Make sure that it is still appropriate to use RandGenerator in conjunction
+// with std::random_shuffle().
+TEST(RandUtilTest, RandGeneratorForRandomShuffle) {
+  EXPECT_EQ(base::RandGenerator(1), 0U);
+  EXPECT_LE(std::numeric_limits<ptrdiff_t>::max(),
+            std::numeric_limits<int64>::max());
+}