Use persistent ID/names for displays.

ui/base/x/x11_util.h

Index: ui/base/x/x11_util.h
diff --git a/ui/base/x/x11_util.h b/ui/base/x/x11_util.h
index c555d057ffa14bd7c6eb9551d196252459c6065e..fd6267ca5a9f001f3e6a4783e08a2c63ce56c551 100644
--- a/ui/base/x/x11_util.h
+++ b/ui/base/x/x11_util.h
@@ -236,6 +236,21 @@ UI_EXPORT void PutARGBImage(Display* display,
 void FreePicture(Display* display, XID picture);
 void FreePixmap(Display* display, XID pixmap);
 
+// Gets the list of the output displaying device handles via XRandR, and sets to
+// |outputs|.  Returns false if it fails to get the list and |outputs| is
+// cleared.
+UI_EXPORT bool GetOutputDeviceHandles(std::vector<XID>* outputs);
+
+// Gets some useful data from the specified output device, such like
+// manufacturer's ID, serial#, and human readable name. Returns false if it
+// fails to get those data and doesn't touch manufacturer ID/serial#/name.
+// You can pass NULL to |manufacturer_id|, |serial_number|, and
+// |human_readable_name| then it just ignores them.
+UI_EXPORT bool GetOutputDeviceData(XID output,
+                                   uint16* manufacturer_id,
+                                   uint32* serial_number,
+                                   std::string* human_readable_name);
+
 enum WindowManagerName {
   WM_UNKNOWN,
   WM_BLACKBOX,