Allow use of container cbegin() and cend() methods, plus sample uses.

Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none

Committed: https://crrev.com/a234a0774c1ae03eadcfba867891df8f822229f6
Cr-Commit-Position: refs/heads/master@{#374827}

[Peter Kasting, 2016-02-05 01:17:37]

pkasting@chromium.org changed reviewers:
+ danakj@chromium.org

[Peter Kasting, 2016-02-05 01:17:37]

After saying I didn't have a personal reason to use these, the very next night
while reading through my new copy of Effective Modern C++ I discovered a whole
item encouraging their use!

Since you said you'd be fine with these in principle, here's a CL to allow them,
provide a little bit of motivation, and demonstrate a sample use.

[Peter Kasting, 2016-02-05 01:38:14]

Hmm.  Irritatingly, it looks like libstdc++ 4.6 does not correctly support the
C++11 specs for container erase() methods (which changed from iterator to
const_iterator).  That was apparently fixed for libstdc++ 4.9.  I didn't check
insert(), which changed similarly, so I don't know if that's broken too.

How long are we likely to be stuck with this libstdc++?  If it's a short time, I
would suggest allowing cbegin()/cend() anyway but with a note that they're less
broadly useful until libstdc++ is upgraded.  If it's a long time, I'm less sure.
 WDYT?

[Peter Kasting, 2016-02-10 03:17:21]

Description was changed from

==========
Allow use of container cbegin() and cend() methods, plus sample use.

BUG=none
TEST=none
==========

to

==========
Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of
TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none
==========

[Peter Kasting, 2016-02-10 03:17:22]

pkasting@chromium.org changed reviewers:
+ sky@chromium.org, thakis@chromium.org
- danakj@chromium.org

[Peter Kasting, 2016-02-10 03:20:06]

Uploaded with new sample uses.

sky: Code review

thakis: Style change review.  Dana seemed OK with this on-thread but is OOO
right now, WDYT?  Also, do you think I should put a note in the styleguide that
old libstdc++s don't support erase(const_iterator) yet, or is that just a
distraction?

[sky, 2016-02-10 16:51:24]

LGTM

[Nico, 2016-02-10 16:54:56]

lgtm, this seems "obviously ok" :-)

https://codereview.chromium.org/1675483002/diff/20001/styleguide/c++/c++11.html
File styleguide/c++/c++11.html (right):

https://codereview.chromium.org/1675483002/diff/20001/styleguide/c++/c++11.ht...
styleguide/c++/c++11.html:378: <td>Applies to all containers, not just
<code>vector</code>.  Consider using <code>const_iterator</code> over
<code>iterator</code> where possible for the same reason as using
<code>const</code> variables and functions where possible; see Effective Modern
C++ item 13 for motivation.  <a
href="https://groups.google.com/a/chromium.org/d/topic/cxx/cS83F_buqLM/discussion">Discussion
thread</a></td>
maybe mention that global std::cbegin()/cend() is c++14 and won't work

[Peter Kasting, 2016-02-11 00:44:35]

https://codereview.chromium.org/1675483002/diff/20001/styleguide/c++/c++11.html
File styleguide/c++/c++11.html (right):

https://codereview.chromium.org/1675483002/diff/20001/styleguide/c++/c++11.ht...
styleguide/c++/c++11.html:378: <td>Applies to all containers, not just
<code>vector</code>.  Consider using <code>const_iterator</code> over
<code>iterator</code> where possible for the same reason as using
<code>const</code> variables and functions where possible; see Effective Modern
C++ item 13 for motivation.  <a
href="https://groups.google.com/a/chromium.org/d/topic/cxx/cS83F_buqLM/discussion">Discussion
thread</a></td>
On 2016/02/10 16:54:56, Nico wrote:
> maybe mention that global std::cbegin()/cend() is c++14 and won't work

I added a note about this to the item on non-member begin() and end().

[Peter Kasting, 2016-02-11 00:44:52]

The CQ bit was checked by pkasting@chromium.org

[Peter Kasting, 2016-02-11 00:44:52]

The patchset sent to the CQ was uploaded after l-g-t-m from thakis@chromium.org,
sky@chromium.org
Link to the patchset: https://codereview.chromium.org/1675483002/#ps40001
(title: "Add note about non-member cbegin() and cend().")

[commit-bot: I haz the power, 2016-02-11 00:46:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1675483002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1675483002/40001

[commit-bot: I haz the power, 2016-02-11 01:36:01]

Description was changed from

==========
Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of
TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none
==========

to

==========
Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of
TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none
==========

[commit-bot: I haz the power, 2016-02-11 01:36:05]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-02-16 22:33:49]

Description was changed from

==========
Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of
TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none
==========

to

==========
Allow use of container cbegin() and cend() methods, plus sample uses.

This also fixes a small bug in the histogram recording of
TabStripModelStatsRecorder::ActiveTabChanged() I spotted while doing this.

BUG=none
TEST=none

Committed: https://crrev.com/a234a0774c1ae03eadcfba867891df8f822229f6
Cr-Commit-Position: refs/heads/master@{#374827}
==========

[commit-bot: I haz the power, 2016-02-16 22:33:49]

Patchset 3 (id:??) landed as
https://crrev.com/a234a0774c1ae03eadcfba867891df8f822229f6
Cr-Commit-Position: refs/heads/master@{#374827}