[ios] Made IDC_BACK and IDC_FORWARD safe.

[ios] Made IDC_BACK and IDC_FORWARD safe.

NavigationManager's GoBack() and GoForward() crash if navigation is not
possible. This mirrors NavigationController's behavior so
NavigationManager should only be changed along with
NavigationController.

KeyCommandsProvider sends IDC_FORWARD and IDC_BACK commands without
checking that navigation is possible and app crashes.

There are 2 fully correct options to fix this bug:
1.) Change NavigationManager and NavigationController, so they don't
    crash (which has both pros and cons).
2.) Change KeyCommandsProvider, so it does not send IDC_FORWARD,
    IDC_BACK commands if navigation is not possible.

Correct fix will be tracked in a separate bug (crbug.com/677160), and
this CL simply fixes a crash in the most simplest way w/o touching
Tab class (which will be removed).

BUG=676727
Committed: https://crrev.com/4ace5d8e5ece05349d1545692c2a2639f2d74d72
Cr-Commit-Position: refs/heads/master@{#440773}

[Eugene But (OOO till 7-30), 2016-12-27 18:08:28]

eugenebut@chromium.org changed reviewers:
+ lpromero@chromium.org, marq@chromium.org

[Eugene But (OOO till 7-30), 2016-12-27 18:08:28]

I don't think that this is is very clean change, but there is not much time left
to fix M-56 RBS. Better fix will be tracked in crbug.com/677160

[Eugene But (OOO till 7-30), 2016-12-27 18:10:16]

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

[commit-bot: I haz the power, 2016-12-27 18:10:35]

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, 2016-12-27 18:21:38]

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

[commit-bot: I haz the power, 2016-12-27 18:21:38]

Dry run: This issue passed the CQ dry run.

[marq (ping after 24h), 2016-12-27 18:24:53]

This change LGTM as a bug fix.

On a more general note, I don't think there's anything wrong with fixing bugs
like this in Tab, just because Tab will be going away. The BVC will also be
going away, as will (likely) the use of scalar command_id constants, so every
part of this issue can be expected to be replaced in the next year anyway.

[Eugene But (OOO till 7-30), 2016-12-27 18:44:17]

On 2016/12/27 18:24:53, marq wrote:
> This change LGTM as a bug fix.
> 
> On a more general note, I don't think there's anything wrong with fixing bugs
> like this in Tab, just because Tab will be going away. The BVC will also be
> going away, as will (likely) the use of scalar command_id constants, so every
> part of this issue can be expected to be replaced in the next year anyway.
Thanks! I did not want to fix this in Tab to avoid regressions when Tab goes
away (we should move the fix to KeyCommandsProvider or NavigationManager before
Tab goes away, but still wanted to be careful).

[Eugene But (OOO till 7-30), 2016-12-27 18:44:25]

The CQ bit was checked by eugenebut@chromium.org

[commit-bot: I haz the power, 2016-12-27 18:44:40]

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, 2016-12-27 18:48:13]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1482864265434490,
"parent_rev": "9702e9aad0ebfd330757ad8e6ba3ef7e23572ec1", "commit_rev":
"87be6cbe65f215c8be80a99761e0aac54ba75aed"}

[commit-bot: I haz the power, 2016-12-27 18:48:40]

Description was changed from

==========
[ios] Made IDC_BACK and IDC_FORWARD safe.

NavigationManager's GoBack() and GoForward() crash if navigation is not
possible. This mirrors NavigationController's behavior so
NavigationManager should only be changed along with
NavigationController.

KeyCommandsProvider sends IDC_FORWARD and IDC_BACK commands without
checking that navigation is possible and app crashes.

There are 2 fully correct options to fix this bug:
1.) Change NavigationManager and NavigationController, so they don't
    crash (which has both pros and cons).
2.) Change KeyCommandsProvider, so it does not send IDC_FORWARD,
    IDC_BACK commands if navigation is not possible.

Correct fix will be tracked in a separate bug (crbug.com/677160), and
this CL simply fixes a crash in the most simplest way w/o touching
Tab class (which will be removed).

BUG=676727
==========

to

==========
[ios] Made IDC_BACK and IDC_FORWARD safe.

NavigationManager's GoBack() and GoForward() crash if navigation is not
possible. This mirrors NavigationController's behavior so
NavigationManager should only be changed along with
NavigationController.

KeyCommandsProvider sends IDC_FORWARD and IDC_BACK commands without
checking that navigation is possible and app crashes.

There are 2 fully correct options to fix this bug:
1.) Change NavigationManager and NavigationController, so they don't
    crash (which has both pros and cons).
2.) Change KeyCommandsProvider, so it does not send IDC_FORWARD,
    IDC_BACK commands if navigation is not possible.

Correct fix will be tracked in a separate bug (crbug.com/677160), and
this CL simply fixes a crash in the most simplest way w/o touching
Tab class (which will be removed).

BUG=676727

Review-Url: https://codereview.chromium.org/2605713002
==========

[commit-bot: I haz the power, 2016-12-27 18:48:41]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2017-01-02 15:46:42]

Description was changed from

==========
[ios] Made IDC_BACK and IDC_FORWARD safe.

NavigationManager's GoBack() and GoForward() crash if navigation is not
possible. This mirrors NavigationController's behavior so
NavigationManager should only be changed along with
NavigationController.

KeyCommandsProvider sends IDC_FORWARD and IDC_BACK commands without
checking that navigation is possible and app crashes.

There are 2 fully correct options to fix this bug:
1.) Change NavigationManager and NavigationController, so they don't
    crash (which has both pros and cons).
2.) Change KeyCommandsProvider, so it does not send IDC_FORWARD,
    IDC_BACK commands if navigation is not possible.

Correct fix will be tracked in a separate bug (crbug.com/677160), and
this CL simply fixes a crash in the most simplest way w/o touching
Tab class (which will be removed).

BUG=676727

Review-Url: https://codereview.chromium.org/2605713002
==========

to

==========
[ios] Made IDC_BACK and IDC_FORWARD safe.

NavigationManager's GoBack() and GoForward() crash if navigation is not
possible. This mirrors NavigationController's behavior so
NavigationManager should only be changed along with
NavigationController.

KeyCommandsProvider sends IDC_FORWARD and IDC_BACK commands without
checking that navigation is possible and app crashes.

There are 2 fully correct options to fix this bug:
1.) Change NavigationManager and NavigationController, so they don't
    crash (which has both pros and cons).
2.) Change KeyCommandsProvider, so it does not send IDC_FORWARD,
    IDC_BACK commands if navigation is not possible.

Correct fix will be tracked in a separate bug (crbug.com/677160), and
this CL simply fixes a crash in the most simplest way w/o touching
Tab class (which will be removed).

BUG=676727

Committed: https://crrev.com/4ace5d8e5ece05349d1545692c2a2639f2d74d72
Cr-Commit-Position: refs/heads/master@{#440773}
==========

[commit-bot: I haz the power, 2017-01-02 15:46:43]

Patchset 2 (id:??) landed as
https://crrev.com/4ace5d8e5ece05349d1545692c2a2639f2d74d72
Cr-Commit-Position: refs/heads/master@{#440773}