Fix assert with distiller code caused by r419635.

Fix assert with distiller code caused by r419635.

The change had a bug because previously WebContentsObserver::DidNavigateMainFrame was listened to which is only called for main frame successful navigations. It was switched to WebContentsObserver::DidFinishNavigation so that it can work with PlzNavigate. However that method is called in more situations, so restrict it to maintain the old behavior.

BUG=650472
Committed: https://crrev.com/eeadd3b103a7e13ffb61b630551fc1d92967d8ae
Cr-Commit-Position: refs/heads/master@{#421233}

[jam, 2016-09-27 05:50:56]

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

[commit-bot: I haz the power, 2016-09-27 05:51:11]

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

[jam, 2016-09-27 05:54:40]

The CQ bit was unchecked by jam@chromium.org

[jam, 2016-09-27 05:56:49]

jam@chromium.org changed reviewers:
+ mdjones@chromium.org

[jam, 2016-09-27 05:56:49]

I don't have an Android device setup currently, do you mean verifying if this
fixes it? From inspection it looks like it should. Thanks

[mdjones, 2016-09-27 15:22:49]

On 2016/09/27 05:56:49, jam wrote:
> I don't have an Android device setup currently, do you mean verifying if this
> fixes it? From inspection it looks like it should. Thanks

It works, Thanks! lgtm

[jam, 2016-09-27 16:31:47]

The CQ bit was checked by jam@chromium.org

[commit-bot: I haz the power, 2016-09-27 16:32:13]

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, 2016-09-27 16:37:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-27 16:39:15]

Description was changed from

==========
Fix assert with distiller code caused by r419635.

The change had a bug because previously
WebContentsObserver::DidNavigateMainFrame was listened to which is only called
for main frame successful navigations. It was switched to
WebContentsObserver::DidFinishNavigation so that it can work with PlzNavigate.
However that method is called in more situations, so restrict it to maintain the
old behavior.

BUG=650472
==========

to

==========
Fix assert with distiller code caused by r419635.

The change had a bug because previously
WebContentsObserver::DidNavigateMainFrame was listened to which is only called
for main frame successful navigations. It was switched to
WebContentsObserver::DidFinishNavigation so that it can work with PlzNavigate.
However that method is called in more situations, so restrict it to maintain the
old behavior.

BUG=650472

Committed: https://crrev.com/eeadd3b103a7e13ffb61b630551fc1d92967d8ae
Cr-Commit-Position: refs/heads/master@{#421233}
==========

[commit-bot: I haz the power, 2016-09-27 16:39:16]

Patchset 1 (id:??) landed as
https://crrev.com/eeadd3b103a7e13ffb61b630551fc1d92967d8ae
Cr-Commit-Position: refs/heads/master@{#421233}