(android) Fix for webView window not being destroyed correctly causing memory leak (bug #290)

[PDLMobileApps]

Platforms affected

android

Motivation and Context

This PR fixes #290

Description

A fix for the issue reported in #290 is suggested in the same. I created this pull request after implementing the fix in my own forked repo and verifying it works as intended in Android.

Testing

• Launched the app compiled without the fix on Android and verified the issue is present using the Chrome Inspector (window with about:blank is present after IAB window is closed)
• Compiled the app with the fix and launched it
• Opened an IAB window
• Closed the IAB window and verified the issue is no longer present using the Chrome Inspector (window with about:blank is no longer present after IAB window is closed)
• Repeated the test a few time

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[mosabab]

The code LGT
Thanks for contributing

[dudtlr072]

When will the full version with these fixes be released?

[ndrake]

The call to new String() is unnecessary, consider doing: if (url.equals("about:blank")) {

[marc7000]

When will the next version with these fixes be released?