bug 1242991 correct vpx include path and vpx/svc_context.h visibilty r=glandium

to fix up --with-system-vpx after f442638a.

config/system-headers

@@ -1304,6 +1304,7 @@ QtSparql/qsparqlresult.h
 pixman.h
 #endif
 #if MOZ_NATIVE_LIBVPX==1
+vpx/svc_context.h
 vpx/vpx_codec.h
 vpx/vpx_decoder.h
 vpx/vpx_encoder.h

media/libvpx/sources.mozbuild

@@ -93,7 +93,8 @@ files = {
           'vpx_dsp/x86/variance_avx2.c',
           'vpx_dsp/x86/variance_impl_avx2.c'],
  'ERROR_CONCEALMENT': ['vp8/decoder/error_concealment.c'],
- 'EXPORTS': ['vpx/vp8.h',
+ 'EXPORTS': ['vpx/svc_context.h',
+             'vpx/vp8.h',
              'vpx/vp8cx.h',
              'vpx/vp8dx.h',
              'vpx/vpx_codec.h',

media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9.gyp

@@ -26,7 +26,7 @@
           ],
         }, {
           'include_dirs': [
-            '../../../../../../../libvpx',
+            '$(MOZ_LIBVPX_CFLAGS)',
           ],
 	}],
         ['build_vp9==1', {