Move some more file utils to the base namespace.

base/files/file_util_proxy.cc

Index: base/files/file_util_proxy.cc
diff --git a/base/files/file_util_proxy.cc b/base/files/file_util_proxy.cc
index 5f6d405a905aac60b178ca104683cf68fc900db8..965b489f4939fd2ed07c03c2fa62204a5662380e 100644
--- a/base/files/file_util_proxy.cc
+++ b/base/files/file_util_proxy.cc
@@ -213,7 +213,7 @@ PlatformFileError DeleteAdapter(const FilePath& file_path, bool recursive) {
     return PLATFORM_FILE_ERROR_NOT_FOUND;
   }
   if (!base::DeleteFile(file_path, recursive)) {
-    if (!recursive && !file_util::IsDirectoryEmpty(file_path)) {
+    if (!recursive && !base::IsDirectoryEmpty(file_path)) {
       return PLATFORM_FILE_ERROR_NOT_EMPTY;
     }
     return PLATFORM_FILE_ERROR_FAILED;