Move bit_cast from base/macros.h to its own header

net/quic/test_tools/mock_random.cc

 // Copyright (c) 2012 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 "net/quic/test_tools/mock_random.h"
 
+#include <string.h>
+
 namespace net {
 namespace test {
 
 MockRandom::MockRandom() : base_(0xDEADBEEF), increment_(0) {}
 
 MockRandom::MockRandom(uint32_t base) : base_(base), increment_(0) {}
 
 void MockRandom::RandBytes(void* data, size_t len) {
   memset(data, 'r' + increment_, len);
 }
 
 uint64_t MockRandom::RandUint64() {
   return base_ + increment_;
 }
 
 void MockRandom::Reseed(const void* additional_entropy, size_t entropy_len) {}
 
 void MockRandom::ChangeValue() {
   increment_++;
 }
 
 }  // namespace test
 }  // namespace net