Simplify IdentityMap.

Simplify IdentityMap.

This removes the requirement for handles as arguments, but also removes
concurrency support, which is not being used at the moment.

Supporting concurrency could be done by introducing a sibling class to
IdentityMap that includes RelocationLock on method calls.

R=bmeurer@chromium.org, ulan@chromium.org

Committed: https://crrev.com/05a60095446f36399208be2041f5a51e63d34bbe
Cr-Commit-Position: refs/heads/master@{#31510}

[Yang, 2015-10-23 08:21:30]

Benedikt, this is what we talked about.
Ulan, please look at the heap changes.

[Yang, 2015-10-23 08:21:35]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-23 08:21:37]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1419563004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1419563004/1

[commit-bot: I haz the power, 2015-10-23 08:44:01]

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

[commit-bot: I haz the power, 2015-10-23 08:44:02]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2015-10-23 09:07:22]

lgtm

[ulan, 2015-10-23 09:57:31]

heap part lgtm

[Yang, 2015-10-23 10:31:22]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-10-23 10:31:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1419563004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1419563004/1

[commit-bot: I haz the power, 2015-10-23 10:32:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-23 10:33:24]

Patchset 1 (id:??) landed as
https://crrev.com/05a60095446f36399208be2041f5a51e63d34bbe
Cr-Commit-Position: refs/heads/master@{#31510}