avoid GCC content::CacheStorage::kSizeUnknown redeclaration error

content/browser/cache_storage/cache_storage_index_unittest.cc

 // Copyright 2016 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 "content/browser/cache_storage/cache_storage_index.h"
 
 #include <list>
 #include <utility>
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 25 matching lines @@
   ASSERT_EQ(3u, index.ordered_cache_metadata().size());
   EXPECT_EQ(1031, index.GetStorageSize());
 
   EXPECT_TRUE(index.SetCacheSize("baz", 2000));
   EXPECT_EQ(2031, index.GetStorageSize());
 
   EXPECT_FALSE(index.SetCacheSize("baz", 2000));
   EXPECT_EQ(2031, index.GetStorageSize());
 
   EXPECT_EQ(2000, index.GetCacheSize("baz"));
-  EXPECT_EQ(CacheStorage::kSizeUnknown, index.GetCacheSize("<not-present>"));
+  EXPECT_EQ(kCacheStorageSizeUnknown, index.GetCacheSize("<not-present>"));
 }
 
 TEST_F(CacheStorageIndexTest, TestDoomCache) {
   CacheStorageIndex index;
   index.Insert(CacheStorageIndex::CacheMetadata("foo", 12));
   index.Insert(CacheStorageIndex::CacheMetadata("bar", 19));
   index.Insert(CacheStorageIndex::CacheMetadata("baz", 1000));
   EXPECT_EQ(3u, index.num_entries());
   ASSERT_EQ(3u, index.ordered_cache_metadata().size());
   EXPECT_EQ(1031, index.GetStorageSize());
@@ skipping 98 matching lines @@
   it++;
   EXPECT_EQ("baz", it->name);
   EXPECT_EQ(1000u, it->size);
 
   EXPECT_EQ(3u, index2.num_entries());
   ASSERT_EQ(3u, index2.ordered_cache_metadata().size());
   EXPECT_EQ(1031, index2.GetStorageSize());
 }
 
 }  // namespace content