Add a filesystem type for DriveFS.

For DriveFS, most operations are handled as native file operations.
However, some operations require special-casing; for those we need a
custom filesystem implementation to override those implementations.

Bug: 874314
Change-Id: I91fffdfb260d6dc53241eed13b734f2df8354f8a
Reviewed-on: https://chromium-review.googlesource.com/1180829
Commit-Queue: Sam McNally <[email protected]>
Reviewed-by: Naoki Fukino <[email protected]>
Reviewed-by: Hiroki Nakagawa <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#584626}
diff --git a/chrome/browser/platform_util_unittest.cc b/chrome/browser/platform_util_unittest.cc
index 7954ccc..528c97db 100644
--- a/chrome/browser/platform_util_unittest.cc
+++ b/chrome/browser/platform_util_unittest.cc
@@ -58,7 +58,8 @@
     // New FileSystemBackend that uses our MockSpecialStoragePolicy.
     additional_backends->push_back(
         std::make_unique<chromeos::FileSystemBackend>(
-            nullptr, nullptr, nullptr, nullptr, nullptr, external_mount_points,
+            nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+            external_mount_points,
             storage::ExternalMountPoints::GetSystemInstance()));
   }
 };