Fix some non-const ref function argument types.

net/disk_cache/backend_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 <stdint.h>
 
 #include "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 45 matching lines @@
 #define CACHE_UMA_BACKEND_IMPL_OBJ backend_
 
 using base::Time;
 
 namespace {
 
 const char kExistingEntryKey[] = "existing entry key";
 
 std::unique_ptr<disk_cache::BackendImpl> CreateExistingEntryCache(
     const base::Thread& cache_thread,
-    base::FilePath& cache_path) {
+    const base::FilePath& cache_path) {
   net::TestCompletionCallback cb;
 
   std::unique_ptr<disk_cache::BackendImpl> cache(new disk_cache::BackendImpl(
       cache_path, cache_thread.task_runner(), NULL));
   int rv = cache->Init(cb.callback());
   if (cb.GetResult(rv) != net::OK)
     return std::unique_ptr<disk_cache::BackendImpl>();
 
   disk_cache::Entry* entry = NULL;
   rv = cache->CreateEntry(kExistingEntryKey, &entry, cb.callback());
@@ skipping 4008 matching lines @@
   disk_cache::SimpleBackendImpl::FlushWorkerPoolForTesting();
   base::RunLoop().RunUntilIdle();
 
   disk_cache::Entry* reopen_entry1;
   ASSERT_THAT(OpenEntry(key1, &reopen_entry1), IsOk());
 
   // This shouldn't pick up entry2's write time incorrectly.
   EXPECT_LE(reopen_entry1->GetLastModified(), entry1_timestamp);
   reopen_entry1->Close();
 }