Use IDL argument default values in modules/encoding/

Use IDL argument default values in modules/encoding/

Replace bogus 'null' default values for DOMString/ScalarValueString
arguments with the actual default values from the spec, and remove the
handling of null strings in the C++ implementation.

BUG=258153
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176934

[Jens Widell, 2014-06-25 06:32:37]

PTAL

[jsbell, 2014-06-25 14:11:06]

lgtm

[Jens Widell, 2014-06-25 14:12:51]

On 2014/06/25 14:11:06, jsbell (on vacation) wrote:
> lgtm

Thanks!

Don't forget to be on vacation. :-)

[Jens Widell, 2014-06-25 14:24:25]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2014-06-25 14:25:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jl@opera.com/356703002/1

[commit-bot: I haz the power, 2014-06-25 15:47:33]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/13547)

[commit-bot: I haz the power, 2014-06-25 16:52:09]

Change committed as 176934