Short answer: no I don't know how to see per-app data usage when using ABP.
Long answer:
I'm running rooted 4.1.2 on a Samsung Galaxy Ace 2 (GT-I8160) and I've deleted or frozen most of the bloatware with Titanium Backup and configured auto-update off and syncing off for everything that's left. So I can run a browser test with ABP on and off without other apps chewing up background data and invalidating the results. The Android OS used about 10KB of data on each test run and Google Services used about 1KB; all other data usage was either ABP or the stock Android browser 'Internet'.
Test procedure:
- Wi-fi off.
- Open browser, load about:blank, clear cache & history & cookies, exit browser.
- Take first set of data usage readings. (Settings - Data Usage)
- Open browser, load www.theregister.co.uk from bookmark. Wait for full page load.
- Back button to about:blank, clear cache & history & cookies, exit via Home button.
- Take second set of data usage readings.
- Toggle ABP filtering on or off and repeat from step 4.
I did 8 tests, alternating bewtween ABP on and off each time. Here are the results:
ABP on
- Browser used 40KB and ABP used 350KB. Total 390KB.
- Browser used 40KB and ABP used 380KB. Total 420KB.
- Browser used 50KB and ABP used 360KB. Total 410KB.
- Browser used 40KB and ABP used 350KB. Total 390KB.
ABP off
- Browser used 620KB and ABP used none. Total 620KB.
- Browser used 530KB and ABP used none. Total 530KB.
- Browser used 490KB and ABP used none. Total 490KB.
- Browser used 520KB and ABP used none. Total 520KB.
I don't know what the 40 to 50KB browser data usage when ABP is on represents. It cannot be the actual volume of data flowing from ABP to the browser. The Register's home page is 53KB of HTML source; that's ignoring all the linked images, scripts, CSS, etc. The true size of the page with all that stuff in is much larger; the web archive my desktop browser generates when I save that page is 681KB. Note that I am running ABP in my desktop browser.
I can only assume that the browser is managing to bypass ABP for some small number of its data requests; perhaps for those on non-standard port numbers. I'm definitely not seeing the real data usage of the browser; that should be around the same size as ABP's data usage during my test runs.
ABP needs a stats facility that reports the data usage of each app that is using it. Unfortunately it doesn't seem to have one. On the plus side, it is reducing total data usage according to my tests. Page loading was quicker too.