Replace base::Callback with base::OnceCallback in base::PendingTask

After this CL, PendingTask holds the posted task as OnceClosure. And to
do that, PendingTasks get non-const on a task invocation, due to the
mutation the posted task for the consumption by the task invocation.

BUG=554299

Review-Url: https://codereview.chromium.org/2386653002
Cr-Commit-Position: refs/heads/master@{#425318}


CrOS-Libchrome-Original-Commit: 739ffe3fd7b83bcb9ef7eb2e4b5c52fdbf35f59d
11 files changed
tree: ac24c1205c44e53eb881a389bb8e98ae63acc10c
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/