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

Revert of Add support for deleting non preceeding surrounding text in chrome.input.ime.deleteSurroundingText (patchset #1 id:1 of https://codereview.chromium.org/851333002/)

Reason for revert:
This cl caused regression that the backspace-to-decommit feature for both VK and physical keyboard autocorrect.

Original issue's description:
> 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}

TBR=nona@chromium.org,bshe@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=446249
Committed: https://crrev.com/7f17a7758881aa33e8790494b170962bc37e05d8
Cr-Commit-Position: refs/heads/master@{#312304}

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

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

[bshe, 2015-01-26 16:09:59]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/868663005/ by bshe@chromium.org.

The reason for reverting is: The regression is fixed in the extension code. It
should be safe to land this again..