RefCountInterface: Make AddRef() and Release() const

RefCountInterface: Make AddRef() and Release() const

This CL makes AddRef() and Release() const member methods and the refcount integer mutable. This is reasonable, because they only manage the lifetime of the object, and this is also how it's done in Chromium.

The purpose is to be able to capture a const pointer in a scoped_refptr, which is currenty impossible. The practial problem this CL solves is this:

void Foo::Bar() const {}

rtc::Callback0<void> Foo::MakeClosure() const {
  return rtc::Bind(&Foo::Bar, this);
}

We currently capture |this| as const Foo*. With this CL, |this| will be captured as scoped_refptr<const Foo>.

A test is also added in bind_unittest to check this behaviour.

BUG=webrtc:5065
R=perkj@webrtc.org, tommi@webrtc.org

Committed: https://crrev.com/1b40a9a8afe0d7b2244ad8dea19e8222fec3c207
Cr-Commit-Position: refs/heads/master@{#10253}

[magjed_webrtc, 2015-10-12 11:27:10]

magjed@webrtc.org changed reviewers:
+ perkj@webrtc.org, tommi@webrtc.org

[magjed_webrtc, 2015-10-12 11:27:55]

Please take a look.

[tommi, 2015-10-12 11:50:15]

lgtm

[perkj_webrtc, 2015-10-12 11:51:16]

On 2015/10/12 11:50:15, tommi (webrtc) wrote:
> lgtm

lgtm

[perkj_webrtc, 2015-10-12 11:51:19]

On 2015/10/12 11:50:15, tommi (webrtc) wrote:
> lgtm

lgtm

[magjed_webrtc, 2015-10-12 11:53:21]

The CQ bit was checked by magjed@webrtc.org

[commit-bot: I haz the power, 2015-10-12 11:53:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1403683004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1403683004/1

[commit-bot: I haz the power, 2015-10-12 13:07:52]

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

[commit-bot: I haz the power, 2015-10-12 13:07:52]

Try jobs failed on following builders:
  mac_x64_rel on tryserver.webrtc (JOB_TIMED_OUT, no build URL)

[magjed_webrtc, 2015-10-12 13:50:57]

Committed patchset #1 (id:1) manually as
1b40a9a8afe0d7b2244ad8dea19e8222fec3c207 (presubmit successful).

[commit-bot: I haz the power, 2015-10-12 13:51:05]

Patchset 1 (id:??) landed as
https://crrev.com/1b40a9a8afe0d7b2244ad8dea19e8222fec3c207
Cr-Commit-Position: refs/heads/master@{#10253}