[InputEvent] Move attributes from |EditCommand| to |CompositeEditCommand| (2/11)

[InputEvent] Move attributes from |EditCommand| to |CompositeEditCommand| (2/11)

This CL moved/added 4 |InputEvent| related attributes to |CompositeEditCommand|:
1. |inputType()|
2. |textDataForInputEvent()|
3. |dataTransferForInputEvent()|
4. |targetRangesForInputEvent()|
And introduced utility |isComposingFromCommand()|.

Reasoning:
|CompositeEditCommand| is more suitable for |InputEvent| as we never fire
'beforeinput' from |SimpleEditCommand|.

This CL doesn't have behavior change.

Please see bug and the design doc below for the big picture:
https://docs.google.com/a/chromium.org/document/d/1M9bQaLKdRpR1qJ9i7zZKN-hKwd4ZkgJs5GPde2ZsDy0/edit?usp=sharing

BUG=678795

[chongz, 2017-01-05 20:30:11]

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

[commit-bot: I haz the power, 2017-01-05 20:30:57]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-05 22:10:00]

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

[commit-bot: I haz the power, 2017-01-05 22:10:01]

Dry run: This issue passed the CQ dry run.

[chongz, 2017-01-05 23:00:35]

Description was changed from

==========
Moved InputEvent attribuates to |CompositeEditCommand|

BUG=
==========

to

==========
[InputEvent] Move attributes from |EditCommand| to |CompositeEditCommand| (2/11)

This CL moved/added 4 |InputEvent| related attributes to |CompositeEditCommand|:
1. |inputType()|
2. |textDataForInputEvent()|
3. |dataTransferForInputEvent()|
4. |targetRangesForInputEvent()|
And introduced utility |isComposingFromCommand()|.

Reasoning:
|CompositeEditCommand| is more suitable for |InputEvent| as we never fire
'beforeinput' from |SimpleEditCommand|.

This CL doesn't have behavior change.

Please see bug and the design doc below for the big picture:
https://docs.google.com/a/chromium.org/document/d/1M9bQaLKdRpR1qJ9i7zZKN-hKwd...

BUG=678795
==========

[chongz, 2017-01-05 23:40:07]

chongz@chromium.org changed reviewers:
+ xiaochengh@chromium.org

[chongz, 2017-01-05 23:40:07]

PTAL, thanks!

[Xiaocheng, 2017-01-06 02:11:47]

xiaochengh@chromium.org changed reviewers:
+ yosin@chromium.org

[Xiaocheng, 2017-01-06 02:11:47]

lgtm

+yosin

[chongz, 2017-01-09 23:41:13]

yosin@ PTAL, thanks!