Fixes a return type mismatch in suggestions service factory.

Fixes a return type mismatch in suggestions service factory.

Fixes IOSChromeContentSuggestionsServiceFactory::BuildServiceInstanceFor
return types by std::moving them, as the declared return type is a
superclass of the actually returned types.

BUG=None

Committed: https://crrev.com/08cd9d655c6a97c1801d1726cd79657665fbe627
Cr-Commit-Position: refs/heads/master@{#414718}

[stkhapugin, 2016-08-26 14:30:16]

stkhapugin@chromium.org changed reviewers:
+ droger@chromium.org

[stkhapugin, 2016-08-26 14:30:16]

PTAL

[droger, 2016-08-26 14:40:35]

lgtm

Is this causing a failure somewhere?

[stkhapugin, 2016-08-26 14:41:31]

The CQ bit was checked by stkhapugin@chromium.org

[commit-bot: I haz the power, 2016-08-26 14:41:54]

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

[Bernhard Bauer, 2016-08-26 14:57:23]

Uh, I'm confused. According to
https://www.chromium.org/rvalue-references#TOC-6.-std::move-does-not-move-it-...,
a std::move is nothing but a cast to an rvalue reference, so why is that
necessary for the return type to work?

[droger, 2016-08-26 15:00:39]

On 2016/08/26 14:57:23, Bernhard (OOO until Sep 7) wrote:
> Uh, I'm confused. According to
>
https://www.chromium.org/rvalue-references#TOC-6.-std::move-does-not-move-it-...,
> a std::move is nothing but a cast to an rvalue reference, so why is that
> necessary for the return type to work?

This explanation seemed convincing:
http://stackoverflow.com/questions/22018115/converting-stdunique-ptrderived-t...

[stkhapugin, 2016-08-26 15:02:42]

On 2016/08/26 14:57:23, Bernhard (OOO until Sep 7) wrote:
> Uh, I'm confused. According to
>
https://www.chromium.org/rvalue-references#TOC-6.-std::move-does-not-move-it-...,
> a std::move is nothing but a cast to an rvalue reference, so why is that
> necessary for the return type to work?

We're seeing the following failure on downstream bots building this file:

no viable conversion from returned value of type
'unique_ptr<ntp_snippets::ContentSuggestionsService>' to function return type
'unique_ptr<KeyedService>'

where ContentSuggestionsService is a subclass of KeyedService. Returning after
std::move moves the reference to an inferred type of unique_ptr<KeyedService>.

[Bernhard Bauer, 2016-08-26 15:15:32]

On 2016/08/26 15:02:42, stkhapugin wrote:
> On 2016/08/26 14:57:23, Bernhard (OOO until Sep 7) wrote:
> > Uh, I'm confused. According to
> >
>
https://www.chromium.org/rvalue-references#TOC-6.-std::move-does-not-move-it-...,
> > a std::move is nothing but a cast to an rvalue reference, so why is that
> > necessary for the return type to work?
> 
> We're seeing the following failure on downstream bots building this file:
> 
> no viable conversion from returned value of type
> 'unique_ptr<ntp_snippets::ContentSuggestionsService>' to function return type
> 'unique_ptr<KeyedService>'
> 
> where ContentSuggestionsService is a subclass of KeyedService. Returning after
> std::move moves the reference to an inferred type of unique_ptr<KeyedService>.

Huh, ok. Thanks both! and LGTM.

[commit-bot: I haz the power, 2016-08-26 15:29:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-26 15:32:12]

Description was changed from

==========
Fixes a return type mismatch in suggestions service factory.

Fixes IOSChromeContentSuggestionsServiceFactory::BuildServiceInstanceFor
return types by std::moving them, as the declared return type is a
superclass of the actually returned types.

BUG=None
==========

to

==========
Fixes a return type mismatch in suggestions service factory.

Fixes IOSChromeContentSuggestionsServiceFactory::BuildServiceInstanceFor
return types by std::moving them, as the declared return type is a
superclass of the actually returned types.

BUG=None

Committed: https://crrev.com/08cd9d655c6a97c1801d1726cd79657665fbe627
Cr-Commit-Position: refs/heads/master@{#414718}
==========

[commit-bot: I haz the power, 2016-08-26 15:32:13]

Patchset 1 (id:??) landed as
https://crrev.com/08cd9d655c6a97c1801d1726cd79657665fbe627
Cr-Commit-Position: refs/heads/master@{#414718}