Disable "using base::FilePath" on Linux since it now compiles.

chrome/installer/util/create_reg_key_work_item.cc

Index: chrome/installer/util/create_reg_key_work_item.cc
diff --git a/chrome/installer/util/create_reg_key_work_item.cc b/chrome/installer/util/create_reg_key_work_item.cc
index 9b9aa9b7c944ef9ad1861ac6aeab53a640470d83..56c3571c56034e2f7227d24433f679fe9ca2a2e1 100644
--- a/chrome/installer/util/create_reg_key_work_item.cc
+++ b/chrome/installer/util/create_reg_key_work_item.cc
@@ -17,11 +17,12 @@ namespace {
 
 // TODO: refactor this because it is only used once.
 void UpOneDirectoryOrEmpty(std::wstring* dir) {
-  FilePath path = FilePath::FromWStringHack(*dir);
-  FilePath directory = path.DirName();
+  base::FilePath path = base::FilePath::FromWStringHack(*dir);
+  base::FilePath directory = path.DirName();
   // If there is no separator, we will get back kCurrentDirectory.
   // In this case, clear dir.
-  if (directory == path || directory.value() == FilePath::kCurrentDirectory)
+  if (directory == path || directory.value() ==
+      base::FilePath::kCurrentDirectory)
     dir->clear();
   else
     *dir = directory.value();