clean up code at crypto folder.

crypto/secure_hash_unittest.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 "crypto/secure_hash.h"
 
+#include <string>
+
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/pickle.h"
 #include "crypto/sha2.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 TEST(SecureHashTest, TestUpdate) {
   // Example B.3 from FIPS 180-2: long message.
   std::string input3(500000, 'a');  // 'a' repeated half a million times
   int expected3[] = { 0xcd, 0xc7, 0x6e, 0x5c,
@@ skipping 47 matching lines @@
 
   PickleIterator data_iterator(pickle);
   EXPECT_TRUE(ctx2->Deserialize(&data_iterator));
   ctx2->Update(input4.data(), input4.size());
   ctx2->Update(input5.data(), input5.size());
 
   ctx2->Finish(output2, sizeof(output2));
 
   EXPECT_EQ(0, memcmp(output1, output2, crypto::kSHA256Length));
 }