Introduce a file-manager-new-ui flag for the new UI of Files.app.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 1ad490584bc6da4a55dd367c112b4a945db9ab19..8ee001b1788ec547bb37b77bcec028eb2a845f02 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1618,6 +1618,9 @@ const char kEnterpriseEnrollmentModulusLimit[] =
 // Loads the File Manager as a packaged app.
 const char kFileManagerPackaged[]           = "file-manager-packaged";
 
+// Loads the File Manager with the new UI.
+const char kFileManagerNewUI[]              = "file-manager-new-ui";
+
 #ifndef NDEBUG
 // Skips all other OOBE pages after user login.
 const char kOobeSkipPostLogin[]             = "oobe-skip-postlogin";