handle PermissionRequests in the WebChromeClient

[adamkobor]

The idea behind this PR is to be capable of handling permission requests coming from the webview on Android. These are vital, if you would like to play DRM protected content inside of it, for example.
The requested resources could be divided into two different groups: the ones where we have a native Android permission as a counterpart, and the ones where we don't.
Where we don't have counterparts (midi sysex messages + protected media), we can use the newly introduced configuration properties inside AndroidWebSettings to automatically grant or deny the requested resources. On the other hand, where we have a counterpart for the requested resource, we check if the desired permission is already granted and if so, then we grant the requested resource too.

What do you think @KevinnZou, would it make sense to have a dedicated section about this new functionality in the README?

[KevinnZou]

@adamkobor Thanks for your contribution! You did a great job! Could you also provide a test sample or a test URL?

[adamkobor]

@KevinnZou ofc!
I've provided two examples and added a block to the readme too in 3d5f6ec

Midi test page without enabling MIDI sysex messages:

Enabled:

DRM disabled:

DRM enabled:

[KevinnZou]

@adamkobor Thanks for your contribution. One thing I want to check is whether the iOS side will encounter the same problem. It would be better to make this feature compatible with both platforms.

[adamkobor]

@adamkobor Thanks for your contribution. One thing I want to check is whether the iOS side will encounter the same problem. It would be better to make this feature compatible with both platforms.

@KevinnZou iOS doesn't have this problem, the EME APIs are enabled there by default, for example. Generally, AFAIK there is no such thing there like the permission requests on Android

[adamkobor]

@KevinnZou do you have an ETA for the release of this? I'm asking because we're depending on this fix in our production code, and we have to use our own fork in between, but this is far from ideal, so we would like to switch back to your lib as soon as possible :)

[KevinnZou]

@adamkobor I have released an alpha version of it, which also updates the CMP version to 1.7.0-beta01. You can use that version first, and I will release the stable version when CMP 1.7.0 is released. Sorry for the delay.