… closed (by invoking ref.close()) causing memory leaks

Platforms affected

Android

Motivation and Context

Fixes open issue 290

Description

When a web view is closed its resources are deallocated (Android).

Testing

Tested by ensuring memory was deallocated and closed web view no longer displayed when inspecting with chrome inspector.

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