Refactored the call box tree BUG=chromium:272493 TEST=run_all_tests.py Change-Id: I688aaa705bc923f9af97161401b787526de05d46 Reviewed-on: https://chromium-review.googlesource.com/182870 Reviewed-by: Ben Chan <[email protected]> Tested-by: Byron Kubert <[email protected]> Commit-Queue: Byron Kubert <[email protected]>