- Remove redundant "impl()->".
- Remove NewBlock method from "impl()", exists in "factory()".
- Resolve TODO comments.

R=adamk@chromium.org, marja@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2345103003
Cr-Commit-Position: refs/heads/master@{#39496}