Add a script to measure CPU time during app link startup.

[mstange]

This script kills all browsers, then launches the browser with a VIEW intent for a URL, waits a fixed number of seconds, and then checks the elapsed CPU time across all processes matching the provided package name.

For example, here we can see that Firefox used 35 seconds of CPU time across its processes during the first 10 seconds of wall clock time when launching a fresh instance to go to cnn.com:

% python3 startup_cpu.py -p org.mozilla.fenix -u https://cnn.com -t 10
Successfully killed process org.mozilla.fenix
Successfully killed process org.mozilla.fenix:tab24
Successfully killed process org.mozilla.fenix:gpu
Successfully killed process org.mozilla.fenix:tab3
Successfully killed process org.mozilla.fenix:media
Successfully killed process org.mozilla.fenix:utility
no processes matching com.android.chrome found, not killing any
no processes matching org.chromium.chrome found, not killing any
Waiting for three seconds.
Launching app.
Starting: Intent { act=android.intent.action.VIEW dat=https://cnn.com/... cmp=org.mozilla.fenix/.IntentReceiverActivity }
Waiting for 10.000000 seconds.
Gathering stats.
Total CPU time: 35 seconds

[MarcLeclair]

👍 works for me locally as well.