Make delete API consistent for String objects

Make delete API consistent for String objects

Deleting an in-bounds character index from a String object should always return
false.

BUG=
LOG=N

Committed: https://crrev.com/d62425b5dfcc2d1b6cdfde97fff28a4d19c75e09
Cr-Commit-Position: refs/heads/master@{#28592}

[conradw, 2015-05-22 11:26:58]

Patchset #1 (id:1) has been deleted

[conradw, 2015-05-22 12:34:59]

conradw@chromium.org changed reviewers:
+ rossberg@chromium.org

[conradw, 2015-05-22 12:34:59]

PTAL

[rossberg, 2015-05-22 12:43:46]

lgtm

[conradw, 2015-05-22 12:50:46]

The CQ bit was checked by conradw@chromium.org

[commit-bot: I haz the power, 2015-05-22 12:51:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1153673003/20001

[commit-bot: I haz the power, 2015-05-22 13:09:18]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-05-22 13:09:25]

Patchset 1 (id:??) landed as
https://crrev.com/d62425b5dfcc2d1b6cdfde97fff28a4d19c75e09
Cr-Commit-Position: refs/heads/master@{#28592}