message: Explicitly forbid dynamic_cast
  After discussion on webrtc-core, this option is still thought to be
  a Bad Idea in webrtc.
  Cr-Commit-Position: refs/heads/main@{#38555}
diff: @@ -173,6 +173,16 @@ headers you need.
  [goog-forward-declarations]: https://google.github.io/styleguide/cppguide.html#Forward_Declarations
  +### RTTI and dynamic_cast
  +
  +The Google style guide [permits the use of dynamic_cast](https://google.github.io/styleguide/cppguide.html#Run-Time_Type_Information__RTTI_).
  +
  +However, WebRTC does not permit it. WebRTC (and Chrome) is compiled with the
  +-fno-rtti flag, and the overhead of enabling RTTI it is on the order of 220
  +Kbytes (for Android Arm64).
  +
  +Use static_cast and take your own steps to ensure type safety.
  +
  ## C
  There's a substantial chunk of legacy C code in WebRTC, and a lot of it is old
  