Bug 957784: Mark gfx/layers as FAIL_ON_WARNINGS. r=nical

gfx/layers/moz.build

@@ -303,6 +303,8 @@ IPDL_SOURCES = [
     'ipc/PTexture.ipdl',
 ]
 
+FAIL_ON_WARNINGS = True
+
 MSVC_ENABLE_PGO = True
 
 include('/ipc/chromium/chromium-config.mozbuild')