Description: Upstream doesn't use gcc. The gcc in Trusty- doesn't have stdatomic.h
  See https://bugs.launchpad.net/oxide/+bug/1668614

--- a/third_party/ffmpeg/libavutil/cpu.c
+++ b/third_party/ffmpeg/libavutil/cpu.c
@@ -20,6 +20,9 @@
 // Chromium: Windows doesn't provide stdatomic.h, so use the compat version.
 #if defined(_MSC_VER)
 #include <compat/atomics/win32/stdatomic.h>
+// Ubuntu 14.04 gcc doesn't provide stdatomic.h, so use the compat version
+#elif defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ == 8
+#include <compat/atomics/gcc/stdatomic.h>
 #else
 #include <stdatomic.h>
 #endif
