Migrate PageSets to StorySets in CT page sets
Migrate PageSets to StorySets in CT page sets

This CL contains changes similar to https://codereview.chromium.org/1203433002/

BUG=skia:3968

Review URL: https://codereview.chromium.org/1201183002

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