[fsp] Store mounted file systems in preferences.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 8d55da43dc21eafc239f3892f12d8ac9810a0374..75f4931c6ecb35bc9fe83eb1dc30fb69d72665ec 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -866,6 +866,10 @@ const char kTimeOnOobe[] = "settings.time_on_oobe";
 // The app/extension name who sets the current wallpaper. If current wallpaper
 // is set by the component wallpaper picker, it is set to an empty string.
 const char kCurrentWallpaperAppName[] = "wallpaper.app.name";
+
+// List of mounted file systems via the File System Provider API. Used to
+// restore them after a reboot.
+const char kFileSystemProviderMounted[] = "file_system_provider.mounted";
 #endif  // defined(OS_CHROMEOS)
 
 // The disabled messages in IPC logging.