**Description**

For a DAG that looks like this:

```
A >> B
```

If A fails, B goes into "upstream_failed" state. If a user then marks A "success", B will remain in "upstream_failed" state. It will not automatically start running. This scenario often happens if the failure of A is dealt with outside of Airflow and the user does not want Airflow to run A again. But he usually expect Airflow to run B after A is marked "success".

**Use case / motivation**

After A is marked "success", its downstream tasks B should be cleared automatically and get ready to be scheduled. To avoid changing this behaviour completely, there can be a toggle button next to "Success" that lets the user decide if he wants Airflow to automatically clear downstream tasks that are in "upstream_failed" state.
airflow/www/views.py
"""Customize permission names for FAB's builtin UserInfoEditView."""
    class_permission_name = permissions.RESOURCE_MY_PROFILE
    route_base = "/userinfoeditview"
    method_permission_name = {
        'this_form_get': 'read',
        'this_form_post': 'edit',
    }
    base_permissions = [permissions.ACTION_CAN_EDIT, permissions.ACTION_CAN_READ]
class CustomUserStatsChartView(UserStatsChartView):
    """Customize permission names for FAB's builtin UserStatsChartView."""
    class_permission_name = permissions.RESOURCE_USER_STATS_CHART
    route_base = "/userstatschartview"
    method_permission_name = {
        'chart': 'read',
        'list': 'read',
    }
    base_permissions = [permissions.ACTION_CAN_READ]
class CustomUserLDAPModelView(UserLDAPModelView):
    """Customize permission names for FAB's builtin UserLDAPModelView."""
    class_permission_name = permissions.RESOURCE_MY_PROFILE
    method_permission_name = {
        'userinfo': 'read',
        'list': 'read',
    }
    base_permissions = [
        permissions.ACTION_CAN_READ,
    ]
class CustomUserOAuthModelView(UserOAuthModelView):