PSA: New WebView webexposed tests to run on CQ

[Ashley Newson]

TL;DR: If you make web-visible changes, you may need to update Android WebView's webexposed expectations as you do for other platforms.

We are re-introducing webexposed tests for Android WebView that align closer to other platforms:

• WebView will have both stable and non-stable expectations.
• Expectations will be checked in the commit queue.
• Unstable expectation changes will not require owner approval.
• Starting in 2025Q1, stable expectation changes will require Blink API Owner approval. Before then, whilst we evaluate running the tests in CQ, we will not require owner approval.

If any changes to a WebView expectation file are required, one or both of the following tests will fail and each provide you with patches to apply:

• org.chromium.android_webview.test.WebExposedTest#testGlobalInterfaceListingStable
• org.chromium.android_webview.test.WebExposedTest#testGlobalInterfaceListingUnstable

(crbug.com/381090604)