Bug 1231701 - Add valgrind suppression for uninitialized memory access and leak in old fontconfig. r=njn

build/valgrind/x86_64-redhat-linux-gnu.sup

@@ -39,6 +39,30 @@
    fun:FcPatternObjectInsertElt
    ...
 }
+# With older versions of fontconfig (e.g. 2.8.0 on taskcluster systems),
+# there's an uninitialized memory usage and leak when loading app fonts.
+{
+   Bug 1231701
+   Memcheck:Param
+   write(buf)
+   ...
+   fun:FcDirCacheWrite
+   fun:FcDirCacheScan
+   fun:FcConfigAddDirList
+   fun:FcConfigAppFontAddDir
+   ...
+}
+{
+   Bug 1231701
+   Memcheck:Leak
+   match-leak-kinds: definite
+   fun:malloc
+   fun:FcDirScanConfig
+   fun:FcDirCacheScan
+   fun:FcConfigAddDirList
+   fun:FcConfigAppFontAddDir
+   ...
+}
 # Leaks due to either Gtk+3 or cairo, but Gecko is not directly involved with
 # those cairo interactions.  One suspected cause is Gecko not closing the
 # display to work around a bug in old Gtk+3 versions.  See also bug 1228724.