Bug 1435223 - Increase the size of idstring to avoid a warning r=baku

MozReview-Commit-ID: FFOByQdUa0I

--HG--
extra : rebase_source : 7e6b89920d5b85b4ba137e325e0a05bb96268575

dom/gamepad/linux/LinuxGamepad.cpp

@@ -41,7 +41,7 @@ typedef struct {
   guint source_id;
   int numAxes;
   int numButtons;
-  char idstring[128];
+  char idstring[256];
   char devpath[PATH_MAX];
 } Gamepad;