Move leak_detector_controller to its own directory

This new directory will hold future code that relates to the leak
detector as well.

BUG=chromium:615223
TEST=unit tests pass

Review-Url: https://codereview.chromium.org/2047163002
Cr-Commit-Position: refs/heads/master@{#398648}
8 files changed