Debug message clarifying the problem like `Issue 1060080: Event Network.loadingFinished is not sent when a frame is loaded from another domain`: https://bugs.chromium.org/p/chromium/issues/detail?id=1060080).
It can help users to identify problem with OOPIF easier without digging into the CDP protocol implementation like in the bug `1060080` mentioned above.
To reproduce:
1. Run `DEBUG="puppeteer:frame" NODE_PATH=../ node examples/oopif.js`.
2. Verify the output contains the debug message:
`
puppeteer:frame The frame '...' moved to another session. Out-of-proccess
iframes (OOPIF) are not supported by Puppeteer yet.
https://github.com/puppeteer/puppeteer/issues/2548
`
