Make the error_string parameter a reference instead of a pointer to enforce

Make the error_string parameter a reference instead of a pointer to enforce
that there is actually an object being passed.

BUG=none
TEST=Covered by unit tests

[jochen (gone - plz use gerrit), 2010-01-08 10:52:11]

This patch makes the interfae a bit more robust.

[Paweł Hajdan Jr., 2010-01-08 11:01:55]

Please drop this CL. It's against the style guide, see
<http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Refere...>

[jochen (gone - plz use gerrit), 2010-01-08 11:22:06]

On 2010/01/08 11:01:55, Paweł Hajdan Jr. wrote:
> Please drop this CL. It's against the style guide, see
>
<http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Refere...>

Then let me add at least a DCHECK(error_string) to BlacklistIO::ReadText,
because accessing a possible NULL pointer isn't a good solution either..

[Paweł Hajdan Jr., 2010-01-08 11:36:55]

On 2010/01/08 11:22:06, Jochen Eisinger wrote:
> On 2010/01/08 11:01:55, Paweł Hajdan Jr. wrote:
> > Please drop this CL. It's against the style guide, see
> >
>
<http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Refere...>
> 
> Then let me add at least a DCHECK(error_string) to BlacklistIO::ReadText,
> because accessing a possible NULL pointer isn't a good solution either..

Sounds good.

[jochen (gone - plz use gerrit), 2010-01-08 12:36:28]

On 2010/01/08 11:36:55, Paweł Hajdan Jr. wrote:
> Sounds good.

please review.

[Paweł Hajdan Jr., 2010-01-08 12:47:52]

LGTM