Enable system NSS key slot.

crypto/scoped_test_system_nss_key_slot.h

 // Copyright 2014 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.
 
 #ifndef CRYPTO_SCOPED_TEST_SYSTEM_NSS_KEY_SLOT_H_
 #define CRYPTO_SCOPED_TEST_SYSTEM_NSS_KEY_SLOT_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "crypto/crypto_export.h"
 
+// Forward declaration, from <pk11pub.h>
+typedef struct PK11SlotInfoStr PK11SlotInfo;
+
 namespace crypto {
 
 class ScopedTestNSSDB;
 
 // Opens a persistent NSS software database in a temporary directory and sets
 // the test system slot to the opened database. This helper should be created in
-// tests where no system token is provided by the Chaps module and before
-// InitializeTPMTokenAndSystemSlot is called. Then the opened test database will
-// be used and the initialization continues as if Chaps had provided this test
-// database. In particular, the DB will be exposed by |GetSystemNSSKeySlot| and
-// |IsTPMTokenReady| will return true.
+// tests to fake the system token that is usually provided by the Chaps module.
+// |slot| is exposed through |GetSystemNSSKeySlot| and |IsTPMTokenReady| will
+// return true.
+// |InitializeTPMTokenAndSystemSlot|, which triggers the TPM initialization,
+// does not have to be called if this helper is used.
 // At most one instance of this helper must be used at a time.
 class CRYPTO_EXPORT_PRIVATE ScopedTestSystemNSSKeySlot {
  public:
   explicit ScopedTestSystemNSSKeySlot();
   ~ScopedTestSystemNSSKeySlot();
 
   bool ConstructedSuccessfully() const;
+  PK11SlotInfo* slot() const;
 
  private:
   scoped_ptr<ScopedTestNSSDB> test_db_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedTestSystemNSSKeySlot);
 };
 
 }  // namespace crypto
 
 #endif  // CRYPTO_SCOPED_TEST_SYSTEM_NSS_KEY_SLOT_H_