Add support for deleting non preceeding surrounding text in chrome.input.ime.deleteSurroundingText

Add support for deleting non preceeding surrounding text in chrome.input.ime.deleteSurroundingText

Previously, only text before cursor will be removed regardless the value of
offset. This CL adds support for deleting text after cursor. We want to this
feature in order to implement "set existing word to composition mode" feature
when cursor is moved inside an existing word. We want to be able to remove the
parts of the existing word before cursor and after cursor first and then call
setComposition to set the word to composition mode.

Note: this API tries to comform the API spec of ibus delete_surrounding_text
here: ibus.googlecode.com/svn/docs/ibus-1.5/IBusInputContext.html#IBusInputContext-delete-surrounding-text
A noticible difference is a positive offset value in this API does not take effect.

BUG=446249
Committed: https://crrev.com/756820cb2c42a7b302a16d24909d820ee18dad0e
Cr-Commit-Position: refs/heads/master@{#312113}

[bshe, 2015-01-16 20:59:22]

bshe@chromium.org changed reviewers:
+ nona@chromium.org, shuchen@chromium.org

[bshe, 2015-01-16 21:02:06]

Hey guys.

Do you mind to take a look at this CL? I am in the process of implementing a
feature which requires remove text before and after cursor. The
deleteSurroundingText API seems only support delete texts before cursor due to
restrictions. I am not familiar with the code, but a quick test seems the
restrictions do not exist anymore and we can delete texts both before and after
cursor. Any comment is welcome!

Thanks

Biao

[Seigo Nonaka, 2015-01-18 23:25:34]

LGTM

I'm sorry for my late response.
FYI, this limitation was due to the past implementation of
deleteSurroundingText. It was implemented with sending back space key since
there is not APIs in that era.

Thank you for fixing!

[Shu Chen, 2015-01-19 00:48:51]

lgtm

[bshe, 2015-01-19 14:25:32]

The CQ bit was checked by bshe@chromium.org

[commit-bot: I haz the power, 2015-01-19 14:25:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/851333002/1

[commit-bot: I haz the power, 2015-01-19 15:14:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-19 15:15:36]

Patchset 1 (id:??) landed as
https://crrev.com/756820cb2c42a7b302a16d24909d820ee18dad0e
Cr-Commit-Position: refs/heads/master@{#312113}

[Shu Chen, 2015-01-21 00:47:43]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/821233003/ by shuchen@chromium.org.

The reason for reverting is: This cl caused regression that the
backspace-to-decommit feature for both VK and physical keyboard autocorrect.
.