base: Get rid of a deprecated version of file_util::GetFileExtensionFromPath().

base/file_util.cc

Index: base/file_util.cc
diff --git a/base/file_util.cc b/base/file_util.cc
index 7cf67dd28e169dfb9bfdbeee2ecc1440419ed568..4748f5e20176d1714f40efdc6a242e8ef7fff2a6 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc
@@ -47,15 +47,6 @@ bool EnsureEndsWithSeparator(FilePath* path) {
   return true;
 }
 
-FilePath::StringType GetFileExtensionFromPath(const FilePath& path) {
-  FilePath::StringType file_name = path.BaseName().value();
-  const FilePath::StringType::size_type last_dot =
-      file_name.rfind(kExtensionSeparator);
-  return FilePath::StringType(last_dot == FilePath::StringType::npos ?
-                              FILE_PATH_LITERAL("") :
-                              file_name, last_dot+1);
-}
-
 void InsertBeforeExtension(FilePath* path, const FilePath::StringType& suffix) {
   FilePath::StringType& value =
       const_cast<FilePath::StringType&>(path->value());
@@ -382,9 +373,10 @@ bool Delete(const std::wstring& path, bool recursive) {
   return Delete(FilePath::FromWStringHack(path), recursive);
 }
 std::wstring GetFileExtensionFromPath(const std::wstring& path) {
-  FilePath::StringType extension =
-      GetFileExtensionFromPath(FilePath::FromWStringHack(path));
-  return extension;
+  std::wstring file_name = FilePath(path).BaseName().value();
+  const std::wstring::size_type last_dot = file_name.rfind(kExtensionSeparator);
+  return std::wstring(last_dot == std::wstring::npos ? L""
+                                                     : file_name, last_dot + 1);
 }
 FILE* OpenFile(const std::wstring& filename, const char* mode) {
   return OpenFile(FilePath::FromWStringHack(filename), mode);