Fix memory leaks in PlatformViewsController.java

[dsafa22]

Clear context references to avoid memory leaks

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[chinmaygarde]

cc @blasten

[blasten]

change LGTM, but this needs a test. Would you be able to add one?

[chinmaygarde]

@blasten Do you have guidance on how to test this or if there is an existing test for this component? If not, we can followup separately on setting up a harness and land this as it looks like a real issue.

[chinmaygarde]

The fix seems sound. The presubmit failures are a result of pending rebase. Per Jason, we should take ownership of this PR and land this if the OP is unable to make progress on it.

[blasten]

PlatformViewsController.java is tested in PlatformViewControllerTest.java. Add another test that extends this one.

To check if contextToPlatformView is empty, make it visible to the package (e.g. remove the private modifier), and add @visibleForTesting annotation, then use onDetachedFromJNI() and onPreEngineRestart() to ensure the value is cleared.

[blasten]

This will be fixed via #27915. Thanks for the PR