Move WriteFile and WriteFileDescriptor from file_util to base namespace.

net/disk_cache/block_files_unittest.cc

Index: net/disk_cache/block_files_unittest.cc
diff --git a/net/disk_cache/block_files_unittest.cc b/net/disk_cache/block_files_unittest.cc
index 4a095c992eceebd604fdef3f0b537359fce55e0d..3f0581a6e1dd5f611ee11b8de6ec76548b306fa7 100644
--- a/net/disk_cache/block_files_unittest.cc
+++ b/net/disk_cache/block_files_unittest.cc
@@ -270,7 +270,7 @@ TEST_F(DiskCacheTest, BlockFiles_InvalidFile) {
   char header[kBlockHeaderSize];
   memset(header, 'a', kBlockHeaderSize);
   EXPECT_EQ(kBlockHeaderSize,
-            file_util::WriteFile(filename, header, kBlockHeaderSize));
+            base::WriteFile(filename, header, kBlockHeaderSize));
 
   EXPECT_TRUE(NULL == files.GetFile(addr));