Fix documentation in callback.h

Comments in callback.h were confusing because sample code was
incorrect. Updated sample code to make it consistent with the
documented behavior.

Change-Id: Id42a9465c49b65937d7b34bf8c0b3664085a628f
Reviewed-on: https://chromium-review.googlesource.com/1019870
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552205}

CrOS-Libchrome-Original-Commit: 3947bb6e0509198bd60f801e58050c654cd2ed19
1 file changed
tree: 7f7f54a44bae100b8d342eff4739f3037f21f5c9
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/