Release TabBarTransitionContext when no longer required

Release TabBarTransitionContext when no longer required.

A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, releasing it will save memory during normal browsing.

This change releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so it's not necessary don't need to 
keep the old one around after its been used.

Instruments shows a saving of around 110KB of memory with this
change.

BUG=none

Review-Url: https://codereview.chromium.org/2780253003
Cr-Commit-Position: refs/heads/master@{#460823}
Committed: https://chromium.googlesource.com/chromium/src/+/4cd903e0450bf609707bc83c5d1f4b415bd51fbc

[PL, 2017-03-29 23:07:40]

Description was changed from

==========
A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, we should try and release it when not required.

This CL releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so we don't need to keep the old
one around after its been used.

In experiments with Instruments, I see a saving of around 110KB of
memory with this change (sample size = 5 runs, will attach Instruments
documents if possible).

BUG=none
==========

to

==========
A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, we should try and release it when not required.

This CL releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so we don't need to keep the old
one around after its been used.

In experiments with Instruments, I see a saving of around 110KB of
memory with this change (sample size = 5 runs, will attach Instruments
documents if possible).

BUG=none
==========

[PL, 2017-03-29 23:09:48]

peterlaurens@chromium.org changed reviewers:
+ edchin@chromium.org, jif@chromium.org

[edchin, 2017-03-30 06:20:23]

lgtm.

[jif, 2017-03-30 09:38:41]

On 2017/03/30 06:20:23, edchin wrote:
> lgtm.

lgtm

please update commit message to make it more timeless.

[PL, 2017-03-30 17:56:26]

Description was changed from

==========
A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, we should try and release it when not required.

This CL releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so we don't need to keep the old
one around after its been used.

In experiments with Instruments, I see a saving of around 110KB of
memory with this change (sample size = 5 runs, will attach Instruments
documents if possible).

BUG=none
==========

to

==========
Release TabBarTransitionContext when no longer required.

A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, releasing it will save memory during normal browsing.

This change releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so it's not necessary don't need to 
keep the old one around after its been used.

Instruments shows a saving of around 110KB of memory with this
change.

BUG=none
==========

[PL, 2017-03-30 17:56:37]

The CQ bit was checked by peterlaurens@chromium.org

[commit-bot: I haz the power, 2017-03-30 17:57:11]

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

[commit-bot: I haz the power, 2017-03-30 18:10:29]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1490896597319170, "parent_rev":
"29bb853d07d410286f932802134ff3732777f713", "commit_rev":
"4cd903e0450bf609707bc83c5d1f4b415bd51fbc"}

[commit-bot: I haz the power, 2017-03-30 18:11:12]

Description was changed from

==========
Release TabBarTransitionContext when no longer required.

A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, releasing it will save memory during normal browsing.

This change releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so it's not necessary don't need to 
keep the old one around after its been used.

Instruments shows a saving of around 110KB of memory with this
change.

BUG=none
==========

to

==========
Release TabBarTransitionContext when no longer required.

A TabBarTransitionContext object is always kept around after visiting
the tab bar switcher, releasing it will save memory during normal browsing.

This change releases the transition context object when the dismiss
animation is completed by the tab bar switcher. A new one is created
every time we enter the switcher so it's not necessary don't need to 
keep the old one around after its been used.

Instruments shows a saving of around 110KB of memory with this
change.

BUG=none

Review-Url: https://codereview.chromium.org/2780253003
Cr-Commit-Position: refs/heads/master@{#460823}
Committed:
https://chromium.googlesource.com/chromium/src/+/4cd903e0450bf609707bc83c5d1f...
==========

[commit-bot: I haz the power, 2017-03-30 18:11:12]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/4cd903e0450bf609707bc83c5d1f...