Getting total CPU time of a process
You didn't mention which version of Android you are running, but I believe this will work in most modern versions.  The exact location within the settings may change depending on version and device manufacturer.  

If you go in to Settings -> Battery and then select an app, you get some or all of  the following details:


CPU total time in seconds
Keep awake time in seconds
Data send 
Data received


I believe these details are valid from the last time the device booted.