UserAgent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0

Steps to reproduce the problem:
No steps, this is a feature request.

What is the expected behavior?
When designing an application platform that is completely web-based, webview tags can be used as containers of the different applications, providing isolation, storage, etc. Depending on the contents and the origins of the application inside the webview, we might want to use the webview API to tune the features and permissions inside the tag.

Spatial navigation is important for hardware with no pointer devices, but it is not always required. For example, if we control the web content that is being displayed, we can implement it taking into account the specific input restrictions on the hardware platform. Still, spatial navigation is a must to browse contents that are not under our control, like in a general-purpose browser or social network contents. Ideally, it could even be triggered by users when provided with a set of input options specific to their device.

To be able to use the <webview> tag as a web application container and setup spatial navigation at will depending on the application needs or user choice, we propose the addition of new API for <webview> to check the status of spatial navigation inside the tag, and manage it independently from the spatial navigation status outside the webview or in other webviews. API consists of:

- a new method `setSpatialNavigationEnabled(bool) to enable or disable the feature for a specific webview.
- a new method `isSpatialNavigationEnabled(callback) to check if the feature is enabled or disabled for a specific webview.

The existing `--enable-spatial-navigation` runtime flag, which currently enables the feature in a global way, could be used to decide the default status in newly created webviews.

What went wrong?
Nothing, this is a feature request.

WebStore page: 

Did this work before? N/A 

Chrome version: 69.0.3489.0 (Developer Build) (64-bit)  Channel: n/a
OS Version: Fedora 28
Flash Version: disabled