Move ReadFileToString to the base namespace.

net/url_request/url_fetcher_impl_unittest.cc

Index: net/url_request/url_fetcher_impl_unittest.cc
diff --git a/net/url_request/url_fetcher_impl_unittest.cc b/net/url_request/url_fetcher_impl_unittest.cc
index 7cc1674b181b1453cf48af66a866202a660d84c1..62f627258dbce727d50cac1f9bd1da98a828be6c 100644
--- a/net/url_request/url_fetcher_impl_unittest.cc
+++ b/net/url_request/url_fetcher_impl_unittest.cc
@@ -555,7 +555,7 @@ void URLFetcherPostFileTest::CreateFetcher(const GURL& url) {
 
 void URLFetcherPostFileTest::OnURLFetchComplete(const URLFetcher* source) {
   std::string expected;
-  ASSERT_TRUE(file_util::ReadFileToString(path_, &expected));
+  ASSERT_TRUE(base::ReadFileToString(path_, &expected));
   ASSERT_LE(range_offset_, expected.size());
   uint64 expected_size =
       std::min(range_length_, expected.size() - range_offset_);