Unbreak Chromium build after https://chromium-review.googlesource.com/c/446667/
Unbreak Chromium build after https://chromium-review.googlesource.com/c/446667/

Without this, `gn gen --check` for Chromium would fail with errors like:

  $ gn gen --check out/gn
  ERROR at //cc/resources/video_resource_updater.cc:25:11: Can't include
  this header from here.
  #include "third_party/libyuv/include/libyuv.h"
            ^----------------------------------
  The target:
    //cc:cc
  is including a file from the target:
    //third_party/libyuv:libyuv_internal

  [...]

  Dependency chain (there may also be others):
    //cc:cc -->
    //third_party/libyuv:libyuv --[private]-->
    //third_party/libyuv:libyuv_internal

BUG=libyuv:685, chromium:692600

Change-Id: I5e5bde2f0e4802d70bfd438793eb2460437398ee
Reviewed-on: https://chromium-review.googlesource.com/449934
Reviewed-by: Nico Weber <c0f02d98506190746d1cdcb01be0f37b51e27077@chromium.org>
Reviewed-by: Henrik Kjellander <60c11d3e646624f25a02b88f51d51ca6b7ff7c72@chromium.org>
Commit-Queue: Nico Weber <c0f02d98506190746d1cdcb01be0f37b51e27077@chromium.org>

lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv,lemenkov/libyuv