Base ObserverList: Add basic support for standard C++ iterators.

Also add a support for const_iterator.

The range-based for loop support follows for free.

See the use case in the dependent CL.

BUG=634916

Review-Url: https://codereview.chromium.org/2340583005
Cr-Commit-Position: refs/heads/master@{#424381}


CrOS-Libchrome-Original-Commit: 29025b60361ec76cf02bab720703c66ae8047be9
2 files changed
tree: 1f6af6d01812359fc20d4ed7fc6acbd436a8d4ac
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/