Blink Scheduler: Remove TaskType references from schduler/base.

When scheduler/base will be moved to //base we can't use Blink types.

Bug: 783309
Change-Id: I1d9bada5a08129a885e9fe6d2f75a02c80e03183
Reviewed-on: https://chromium-review.googlesource.com/943565
Reviewed-by: Kentaro Hara <[email protected]>
Reviewed-by: Hajime Hoshi <[email protected]>
Reviewed-by: Alexander Timin <[email protected]>
Commit-Queue: Greg Kraynov <[email protected]>
Cr-Commit-Position: refs/heads/master@{#541408}
14 files changed