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 6c581acde1d210eda620d52870d9284332459f1a..23b0165a040e5a957d21ca290b240012d0ea204f 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1739,6 +1739,10 @@ 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";