Fix 15 coverity complaints....

net/disk_cache/disk_cache_test_base.cc

 // Copyright (c) 2006-2008 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 "net/disk_cache/disk_cache_test_base.h"
 
 #include "net/disk_cache/backend_impl.h"
 #include "net/disk_cache/disk_cache_test_util.h"
 #include "net/disk_cache/mem_backend_impl.h"
 
@@ skipping 47 matching lines @@
 
   if (!implementation_) {
     cache_ = disk_cache::CreateCacheBackend(path, force_creation_, size_,
                                             net::DISK_CACHE);
     return;
   }
 
   InitDiskCacheImpl(path);
 }
 
-void DiskCacheTestWithCache::InitDiskCacheImpl(const std::wstring path) {
+void DiskCacheTestWithCache::InitDiskCacheImpl(const std::wstring& path) {
   if (mask_)
     cache_impl_ = new disk_cache::BackendImpl(path, mask_);
   else
     cache_impl_ = new disk_cache::BackendImpl(path);
 
   cache_ = cache_impl_;
   ASSERT_TRUE(NULL != cache_);
 
   if (size_)
     EXPECT_TRUE(cache_impl_->SetMaxSize(size_));
@@ skipping 25 matching lines @@
   std::wstring path = GetCachePath();
   EXPECT_TRUE(CheckCacheIntegrity(path, new_eviction_));
 
   InitDiskCacheImpl(path);
 }
 
 void DiskCacheTestWithCache::SetTestMode() {
   ASSERT_TRUE(implementation_ && !memory_only_);
   cache_impl_->SetUnitTestMode();
 }