Fixing regression in AOSP CallDetails

A regression was introduced which caused the back arrow in the AOSP
CallDetailsActivity to not work properly.

This CL merges an external contribution (http://pagit/626605) that
fixes the issue by setting the parentActivityName appropriately.

Bug:30004436
Change-Id: I238ff71f3f7e618d5adc972c50012b13f3753f40