Viewer still has plenty of code that uses ImGui to create application
specific UI, but the structural code that forwards input to ImGui, and
converts per-frame ImGui rendering data to Skia draw commands is now in
a single component that can be reused in any sk_app-based application.
Bug: skia:
Change-Id: Ic14ece659d4af8ee13b69c638bdaf7df6c24f5c0
Reviewed-on: https://skia-review.googlesource.com/82627
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
