Add microbenchmark for these methods.
BUG=v8:4663
LOG=N
R=adamk@chromium.org, littledan@chrommium.org

Review URL: https://codereview.chromium.org/1746383003

Cr-Commit-Position: refs/heads/master@{#34556}

BUG=v8:4007
LOG=N
R=arv@chromium.org, rossberg@chromium.org

Review URL: https://codereview.chromium.org/548833002

Cr-Commit-Position: refs/heads/master@{#28270}