Some includes in log.h were only needed by log.cc so move them there.
Some were not needed at all, so remove them completely.

Drive-by cleanup FunctionEvent(), which was never called without args
for the last parameters which had default values.

Change-Id: Id8b0c634c4d39d3c278ab3d932ed7af4142fd9c9
Reviewed-on: https://chromium-review.googlesource.com/c/1425914Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59003}