Remove more usage of the base::ListValue::Append(Value*) overload.

This overload is deprecated: prefer the std::unique_ptr<Value> version,
which helps the compiler enforce that ownership transfer occurs.

BUG=581865
R=danakj@chromium.org
TBR=brettw@chromium.org

Review-Url: https://codereview.chromium.org/2285933003
Cr-Commit-Position: refs/heads/master@{#417396}
28 files changed