diff -up mozilla-release/toolkit/xre/nsAppRunner.cpp.old mozilla-release/toolkit/xre/nsAppRunner.cpp

--- mozilla-release/toolkit/xre/nsAppRunner.cpp.old	2014-11-26 03:17:40.000000000 +0100

+++ mozilla-release/toolkit/xre/nsAppRunner.cpp	2015-01-05 14:23:05.977933308 +0100

@@ -4168,10 +4168,8 @@ XREMain::XRE_main(int argc, char* argv[]

 #if defined(MOZ_WIDGET_GTK)

 #if defined(MOZ_MEMORY) || defined(__FreeBSD__) || defined(__NetBSD__)

-  // Disable the slice allocator, since jemalloc already uses similar layout

-  // algorithms, and using a sub-allocator tends to increase fragmentation.

-  // This must be done before g_thread_init() is called.

-  g_slice_set_config(G_SLICE_CONFIG_ALWAYS_MALLOC, 1);

+  // rhbz#1014858 - enable slice allocator for child processes

+  unsetenv("G_SLICE");

 #endif

   g_thread_init(nullptr);

 #endif