Revert "[TimeStats] Add callback for global stats"

This reverts commit d5065451af373b954ee660d26d0fbf7b68f4c539.

Reason for revert: submission of I6d395237082337a22f37190343a1fc59703d39bf raced with this change's presubmit, causing a build breakage.

Change-Id: I5fbb1b0e93340b6a4cd99e4731d69e0fb17e5c14
7 files changed