TreatReturnedNullStringAs=undefined removed from DataTransfer.idl

TreatReturnedNullStringAs=undefined removed from DataTransfer.idl

DataTransfer::m_dropEffect and ::m_effectAllowed are initialized as
"uninitialized" string. m_dropEffect can only be set via setDropEffect
and only permitted values are: none, copy, link and move; any other
value cannot be set. Similarly for the m_effectAllowed can be only set
via setEffectAllowed, only if the value is either: uninitialized, none,
copy, link, move, copyLink, copyMove, linkMove, all; any other value
cannot be set. For m_dropEffect if the value set is null or undefined,
then it will be set to none and in case of m_effectAllowed it set it to
uninitalized.

Test has been added where empty string, null or undefined results for
m_dropEffect as none and m_effectAllowed as uninitialized.

m_dropEffect should be set as none by default but is set to unintialized
to avoid scenario when m_dropEffect is not set.

BUG=497982
R=philipj, haraken

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197013

[Habib Virji, 2015-06-11 09:16:41]

The CQ bit was checked by habib.virji@samsung.com to run a CQ dry run

[commit-bot: I haz the power, 2015-06-11 09:17:15]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1175223003/1

[commit-bot: I haz the power, 2015-06-11 11:34:00]

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

[commit-bot: I haz the power, 2015-06-11 11:34:01]

Dry run: This issue passed the CQ dry run.

[Habib Virji, 2015-06-11 12:48:06]

The CQ bit was checked by habib.virji@samsung.com

[Habib Virji, 2015-06-11 12:48:08]

The CQ bit was unchecked by habib.virji@samsung.com

[philipj_slow, 2015-06-11 13:07:32]

In addition to noting that no tests broke, please also analyze the
implementation to see if it is possible under any conditions for these to return
null, and mention the conclusion in the description (commit message). I've taken
a quick look like these can't be null, but there may be cases where it can
happen and there just isn't any test coverage.

[Habib Virji, 2015-06-11 16:48:50]

The CQ bit was checked by habib.virji@samsung.com to run a CQ dry run

[commit-bot: I haz the power, 2015-06-11 16:49:00]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1175223003/40001

[Habib Virji, 2015-06-11 16:51:23]

On 2015/06/11 13:07:32, philipj wrote:
> In addition to noting that no tests broke, please also analyze the
> implementation to see if it is possible under any conditions for these to
return
> null, and mention the conclusion in the description (commit message). I've
taken
> a quick look like these can't be null, but there may be cases where it can
> happen and there just isn't any test coverage.

Thanks philips has tried analysing code and see all the calls for setting
m_dropEffect and m_effectAllowed. Has added a description in the commit message
too.  

Have also added test where value when set to "", null, undefined all result in
none or uninitialized for m_dropEffect and m_effectAllowed.

[philipj_slow, 2015-06-11 18:08:24]

I've wrapped the description to 72 columns to make it more readable here and in
git log.

[philipj_slow, 2015-06-11 18:10:15]

LGTM, looks like this will not have any risk of regression at all.

[commit-bot: I haz the power, 2015-06-11 18:16:55]

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

[commit-bot: I haz the power, 2015-06-11 18:16:56]

Dry run: This issue passed the CQ dry run.

[haraken, 2015-06-11 23:25:44]

LGTM

[philipj_slow, 2015-06-12 07:41:11]

The CQ bit was checked by philipj@opera.com

[philipj_slow, 2015-06-12 07:41:12]

lgtm

Sending to CQ

[commit-bot: I haz the power, 2015-06-12 07:41:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1175223003/40001

[commit-bot: I haz the power, 2015-06-12 07:45:02]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197013