[tracing] Mechanical rename of LevelOfDetail enum to enum class.

This CL changes the LevelOfDetail enum to enum class to make it easier
to read the code.

TBR=jochen@chromium.org
BUG=499731

Review URL: https://codereview.chromium.org/1273413002

Cr-Commit-Position: refs/heads/master@{#342404}


CrOS-Libchrome-Original-Commit: 297cae0bc0f633a600bc36c09097540a2c03d7f9
7 files changed
tree: 8a04f1d1226536593968167722fd0d64020fbdb7
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/