HttpProxyCacheServes not works in Android 9

In Android 9,

The ``proxy.getProxyUrl(url);`` return the same url and not cached url.

But it works on Android 4.4-7.

Start by reproducing the Android 9 behavior around proxy.getProxyUrl(url), comparing it with Android 4.4-7 where the URL is cached. Trace why the method returns the original URL on Android 9, then verify that it returns a cached URL without regressing the older Android versions.

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