Add include dirs to dependent targets in the GN build.

This will enable it to be hooked up.

TBR=tomfinegan@chromium.org

Review URL: https://codereview.chromium.org/584253002

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/libvpx@292050 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
1 file changed