Bug 1354166 - Add missing #include for gfxPlatform::IsHeadless(). r=bdahl

MozReview-Commit-ID: DkpUu8j3Lou

toolkit/xre/nsAppRunner.cpp

@@ -89,6 +89,7 @@
 #include "nsIDocShell.h"
 #include "nsAppShellCID.h"
 #include "mozilla/scache/StartupCache.h"
+#include "gfxPlatform.h"
 #include "gfxPrefs.h"
 
 #include "mozilla/Unused.h"