Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

It is invalid to show dialogs on some kinds of WebContents.
WebContentsModalDialogManager::FromWebContents() returns null for these.
However, ConstrainedWindowMac assumes GetDialogManager() returns non-
null.

It's hard to control the myriad of ways a WebContents may want to invoke
a dialog and we currently seem to be missing some likely crashes on Mac
from this. Add a CHECK() so we crash cleanly and quickly.

BUG=674960
Committed: https://crrev.com/cafed52c5f3313646b8e04e05601b5cb98f305b3
Cr-Commit-Position: refs/heads/master@{#439625}

[tapted, 2016-12-19 06:30:18]

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

[commit-bot: I haz the power, 2016-12-19 06:30:31]

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, 2016-12-19 06:46:58]

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

[commit-bot: I haz the power, 2016-12-19 06:46:59]

Dry run: This issue passed the CQ dry run.

[tapted, 2016-12-19 06:58:38]

tapted@chromium.org changed reviewers:
+ rsesek@chromium.org

[tapted, 2016-12-19 06:58:39]

Hi Robert - do you think this will help? 

Of course, the "Stability-Crash-Chronic" in http://crbug.com/629529 needs a fix
too - it might need some more prodding. But I think the signin folks need to
sort out the UX they want for popping a dialog in this case.

[Robert Sesek, 2016-12-19 23:37:22]

LGTM

I think this is probably safer than allowing the current behavior, even if it
does introduce some short-term crashiness.

[tapted, 2016-12-19 23:47:48]

The CQ bit was checked by tapted@chromium.org

[commit-bot: I haz the power, 2016-12-19 23:48:24]

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, 2016-12-19 23:55:45]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1482191268048230, "parent_rev":
"9af280ae3cfa8b486ca65e9b010f46b2c0f66760", "commit_rev":
"493553cb04a708709faf2cd43a39b1956b9027f9"}

[commit-bot: I haz the power, 2016-12-19 23:56:11]

Description was changed from

==========
Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

It is invalid to show dialogs on some kinds of WebContents.
WebContentsModalDialogManager::FromWebContents() returns null for these.
However, ConstrainedWindowMac assumes GetDialogManager() returns non-
null.

It's hard to control the myriad of ways a WebContents may want to invoke
a dialog and we currently seem to be missing some likely crashes on Mac
from this. Add a CHECK() so we crash cleanly and quickly.

BUG=674960
==========

to

==========
Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

It is invalid to show dialogs on some kinds of WebContents.
WebContentsModalDialogManager::FromWebContents() returns null for these.
However, ConstrainedWindowMac assumes GetDialogManager() returns non-
null.

It's hard to control the myriad of ways a WebContents may want to invoke
a dialog and we currently seem to be missing some likely crashes on Mac
from this. Add a CHECK() so we crash cleanly and quickly.

BUG=674960

Review-Url: https://codereview.chromium.org/2589663002
==========

[commit-bot: I haz the power, 2016-12-19 23:56:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-12-19 23:57:50]

Description was changed from

==========
Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

It is invalid to show dialogs on some kinds of WebContents.
WebContentsModalDialogManager::FromWebContents() returns null for these.
However, ConstrainedWindowMac assumes GetDialogManager() returns non-
null.

It's hard to control the myriad of ways a WebContents may want to invoke
a dialog and we currently seem to be missing some likely crashes on Mac
from this. Add a CHECK() so we crash cleanly and quickly.

BUG=674960

Review-Url: https://codereview.chromium.org/2589663002
==========

to

==========
Mac: Add CHECK() in ConstrainedWindowMac::GetDialogManager().

It is invalid to show dialogs on some kinds of WebContents.
WebContentsModalDialogManager::FromWebContents() returns null for these.
However, ConstrainedWindowMac assumes GetDialogManager() returns non-
null.

It's hard to control the myriad of ways a WebContents may want to invoke
a dialog and we currently seem to be missing some likely crashes on Mac
from this. Add a CHECK() so we crash cleanly and quickly.

BUG=674960

Committed: https://crrev.com/cafed52c5f3313646b8e04e05601b5cb98f305b3
Cr-Commit-Position: refs/heads/master@{#439625}
==========

[commit-bot: I haz the power, 2016-12-19 23:57:50]

Patchset 1 (id:??) landed as
https://crrev.com/cafed52c5f3313646b8e04e05601b5cb98f305b3
Cr-Commit-Position: refs/heads/master@{#439625}