[Interpreter] Add tests for adding strings and heap number arithmetic.

[Interpreter] Add tests for adding strings and heap number arithmetic.

BUG=v8:4280
LOG=N

Committed: https://crrev.com/003648772ae53c82c9fbfbe653acd62d61a17c42
Cr-Commit-Position: refs/heads/master@{#30986}

[oth, 2015-09-28 08:42:59]

oth@chromium.org changed reviewers:
+ rmcilroy@chromium.org

[oth, 2015-09-28 08:43:00]

Please take a look at the changes to test-intpreter.cc.

Thanks!

[rmcilroy, 2015-09-28 09:49:13]

Looks great, thanks for doing this! Please fix the typo in the description /
title, but LGTM otherwise.

[oth, 2015-09-28 18:38:33]

The CQ bit was checked by oth@chromium.org

[oth, 2015-09-28 18:38:33]

The patchset sent to the CQ was uploaded after l-g-t-m from
rmcilroy@chromium.org
Link to the patchset: https://codereview.chromium.org/1374613002/#ps40001
(title: "Rebase.")

[commit-bot: I haz the power, 2015-09-28 18:38:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1374613002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1374613002/40001

[commit-bot: I haz the power, 2015-09-28 19:14:24]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-28 19:14:38]

Patchset 3 (id:??) landed as
https://crrev.com/003648772ae53c82c9fbfbe653acd62d61a17c42
Cr-Commit-Position: refs/heads/master@{#30986}