clang/win: Fix most -Wunused-function warnings in Chromium code.

base/files/file_util_unittest.cc

Index: base/files/file_util_unittest.cc
diff --git a/base/files/file_util_unittest.cc b/base/files/file_util_unittest.cc
index 52581f8ce4310a9af5c887831d134ae11c93b795..476ed16c0df8bfe6b2f0bebef8e7d9bef67ce2a6 100644
--- a/base/files/file_util_unittest.cc
+++ b/base/files/file_util_unittest.cc
@@ -244,15 +244,6 @@ std::wstring ReadTextFile(const FilePath& filename) {
   return std::wstring(contents);
 }
 
-#if defined(OS_WIN)
-uint64 FileTimeAsUint64(const FILETIME& ft) {
-  ULARGE_INTEGER u;
-  u.LowPart = ft.dwLowDateTime;
-  u.HighPart = ft.dwHighDateTime;
-  return u.QuadPart;
-}
-#endif
-
 TEST_F(FileUtilTest, FileAndDirectorySize) {
   // Create three files of 20, 30 and 3 chars (utf8). ComputeDirectorySize
   // should return 53 bytes.