Add DriveFS to about:flags.

Also move the DriveFS feature to a more common location in
chromeos/chromeos_features.h.

Bug: 859800
Change-Id: Iffffea69c4874ae0583c67e8a8e6a9b50a4951e4
Reviewed-on: https://chromium-review.googlesource.com/1124211
Reviewed-by: Stuart Langley <[email protected]>
Reviewed-by: Noel Gordon <[email protected]>
Commit-Queue: Sam McNally <[email protected]>
Cr-Commit-Position: refs/heads/master@{#572459}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 0df2628..52f918fe 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -4041,6 +4041,12 @@
      flag_descriptions::kGamepadPollingRateDescription, kOsDesktop,
      MULTI_VALUE_TYPE(kGamepadPollingRateChoices)},
 
+#if defined(OS_CHROMEOS)
+    {"enable-drive-fs", flag_descriptions::kEnableDriveFsName,
+     flag_descriptions::kEnableDriveFsDescription, kOsCrOS,
+     FEATURE_VALUE_TYPE(chromeos::features::kDriveFs)},
+#endif  // OS_CHROMEOS
+
     // NOTE: Adding a new flag requires adding a corresponding entry to enum
     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
     // Histograms" in tools/metrics/histograms/README.md (run the