Change access mode of disk devices when mounting based on config.

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 e55a3fde2394d23958baeed0d38f25ffed94b490..d3a8501a50ebb30251af37090f9ce41dce4e864a 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1748,6 +1748,10 @@ const char kDeviceLocation[] = "device_status.location";
 // storage for the user.
 const char kExternalStorageDisabled[] = "hardware.external_storage_disabled";
 
+// A pref holding the value of the policy used to limit mounting of external
+// storage to read-only mode for the user.
+const char kExternalStorageReadOnly[] = "hardware.external_storage_read_only";
+
 // Copy of owner swap mouse buttons option to use on login screen.
 const char kOwnerPrimaryMouseButtonRight[] = "owner.mouse.primary_right";