fix: Fix JavaScript handlers in InAppBrowser for Android

[fuzzybinary]

Android InAppBrowserActivity would not call prepareAndAddUserScripts when WebViewFeature.DOCUMENT_START_SCRIPT, which would prevent shims like callHandler from being injected.

Fix this by calling prepareAndAddUserScripts during OnCreate.

Other injections were likely also broken but this is the one I needed.

I also added an integration test for JavaScript handlers in in_app_browser. This test fails without this change on Android emulators 33+.

Connection with issue(s)

Resolve issue #1973

Testing and Review Notes

So far as I can tell, we do not need to wrap prepareAndAddUserScripts to check if WebViewFeature.DOCUMENT_START_SCRIPT is supported to prevent a double call, as addPluginScript does this already.

[pichillilorenzo]

This is not related to prepareAndAddUserScripts as it should be called already from InAppWebView.
I found that the issue is related to windowId of InAppBrowserActivity to be not null, actually it is -1 when coming from the Bundle as default value.
Thanks anyway for the help, I'm going to fix it now.

[pichillilorenzo]

@all-contributors please add @fuzzybinary for test

[allcontributors]

@pichillilorenzo

I've put up a pull request to add @fuzzybinary! 🎉