webpages_playback: clean up definition of BENCHMARK_DIR Review URL: https://codereview.appspot.com/6949065
webpages_playback: clean up definition of BENCHMARK_DIR
Review URL: https://codereview.appspot.com/6949065

git-svn-id: 32fc27f4dcfb6c0385cd9719852b95fe6680452d@6844 2bbb7eff-a529-9590-31e7-b0007b416f81

google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot