[heap] Make MarkInlinedFunctionsCode visitor private.

[heap] Make MarkInlinedFunctionsCode visitor private.

Now that the VisitCode visitor is actually marking through to inlined
code objects (as opposed to the VisitJSFunction visitor), we can make
this helper method private again.

R=ulan@chromium.org

Committed: https://crrev.com/aca2176500df5ce5faf41c6720f58b74d38bb825
Cr-Commit-Position: refs/heads/master@{#31860}

[ulan, 2015-11-06 14:38:15]

lgtm, nice!

[Michael Starzinger, 2015-11-06 14:54:47]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-11-06 14:54:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1422853008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1422853008/1

[commit-bot: I haz the power, 2015-11-06 15:18:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-06 15:18:30]

Patchset 1 (id:??) landed as
https://crrev.com/aca2176500df5ce5faf41c6720f58b74d38bb825
Cr-Commit-Position: refs/heads/master@{#31860}