The Android, iOS, and Embedder API all directly make calls on the Engine instead of the shell for SetViewportMetrics and DispatchPointerDataPacket.

In fact, they all use very similar code that looks to be copy-pasted from shell.cc:

https://github.com/flutter/engine/tree/6cf0d1350e0ac03df9ebcbb15c35a4a035010460/shell/platform/embedder/embedder_engine.cc#L82-L115

https://github.com/flutter/engine/blob/6cf0d1350e0ac03df9ebcbb15c35a4a035010460/shell/platform/android/android_shell_holder.cc#L175-L207

https://github.com/flutter/engine/blob/6cf0d1350e0ac03df9ebcbb15c35a4a035010460/shell/platform/darwin/ios/framework/Source/FlutterEngine.mm#L128-L147

We should refactor all of these to use the same path through shell.cc, and ideally make it impossible for embedders to call these methods directly on the engine (which I believe would be breaking).

/cc @chinmaygarde @cbracken @jason-simmons