Revert of Store the next serial number in the function cache rather than in the isolate.

Revert of Store the next serial number in the function cache rather than in the isolate.Don't overwrite existi (patchset #4 id:60001 of https://codereview.chromium.org/988693003/)

Reason for revert:
This doesn't do what it's supposed to do. The problem seems to lie on the blink side, people aren't reusing their FunctionTemplates (or creating them when not necessary).

Original issue's description:
> Don't overwrite existing serial numbers on the function template, otherwise instantiating the function for a new context causes the serial number to bump.
>
> Committed: https://crrev.com/1e638c3610ec6938e5fb16c42018642195782fb2
> Cr-Commit-Position: refs/heads/master@{#27048}

TBR=yangguo@chromium.org,dcarney@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/a9a362360441ab83227d4c84d3e147209999d56a
Cr-Commit-Position: refs/heads/master@{#27067}

[Toon Verwaest, 2015-03-09 10:53:29]

Created Revert of Store the next serial number in the function cache rather than
in the isolate.Don't overwrite existi

[commit-bot: I haz the power, 2015-03-09 10:53:50]

The CQ bit was unchecked by commit-bot@chromium.org

[Yang, 2015-03-09 11:23:24]

On 2015/03/09 10:53:29, Toon Verwaest wrote:
> Created Revert of Store the next serial number in the function cache rather
than
> in the isolate.Don't overwrite existi

lgtm.

[Toon Verwaest, 2015-03-09 12:29:12]

The CQ bit was checked by verwaest@chromium.org

[commit-bot: I haz the power, 2015-03-09 12:29:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/993533003/1

[commit-bot: I haz the power, 2015-03-09 12:30:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-09 12:30:27]

Patchset 1 (id:??) landed as
https://crrev.com/a9a362360441ab83227d4c84d3e147209999d56a
Cr-Commit-Position: refs/heads/master@{#27067}