customtabs: Keep a reference to Tab in PageLoadMetricsObserver, not WebContents.

customtabs: Keep a reference to Tab in PageLoadMetricsObserver, not WebContents.

The lifetime of the PageLoadMetricsObserver in CustomTabActivity is tied
to the tab, not to the WebContents. It makes more sense to capture a
reference to the tab.

This might be related to crbug.com/633186, even though no evidence of
leak was found. Regardless, this makes more sense.

BUG=633186
Committed: https://crrev.com/463006e76317b10db50e6106f60b5dcaa3c3a19f
Cr-Commit-Position: refs/heads/master@{#410615}

[Benoit L, 2016-08-08 14:05:46]

The CQ bit was checked by lizeb@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-08 14:06:01]

Dry run: 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, 2016-08-08 15:12:44]

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

[commit-bot: I haz the power, 2016-08-08 15:12:45]

Dry run: This issue passed the CQ dry run.

[Benoit L, 2016-08-08 15:14:52]

lizeb@chromium.org changed reviewers:
+ yusufo@chromium.org

[Yusuf, 2016-08-08 21:47:19]

lgtm

[Benoit L, 2016-08-09 08:13:50]

The CQ bit was checked by lizeb@chromium.org

[commit-bot: I haz the power, 2016-08-09 08:14:38]

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, 2016-08-09 08:20:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-09 08:21:56]

Description was changed from

==========
customtabs: Keep a reference to Tab in PageLoadMetricsObserver, not WebContents.

The lifetime of the PageLoadMetricsObserver in CustomTabActivity is tied
to the tab, not to the WebContents. It makes more sense to capture a
reference to the tab.

This might be related to crbug.com/633186, even though no evidence of
leak was found. Regardless, this makes more sense.

BUG=633186
==========

to

==========
customtabs: Keep a reference to Tab in PageLoadMetricsObserver, not WebContents.

The lifetime of the PageLoadMetricsObserver in CustomTabActivity is tied
to the tab, not to the WebContents. It makes more sense to capture a
reference to the tab.

This might be related to crbug.com/633186, even though no evidence of
leak was found. Regardless, this makes more sense.

BUG=633186

Committed: https://crrev.com/463006e76317b10db50e6106f60b5dcaa3c3a19f
Cr-Commit-Position: refs/heads/master@{#410615}
==========

[commit-bot: I haz the power, 2016-08-09 08:21:57]

Patchset 1 (id:??) landed as
https://crrev.com/463006e76317b10db50e6106f60b5dcaa3c3a19f
Cr-Commit-Position: refs/heads/master@{#410615}