A quick search of github reveals:
https://github.com/larzeitlin/CombOv...ain_Controls.h
Searching through the WDL-OL git repo history is another option:
git log --diff-filter=D --summary | grep delete
> lists paths of all deleted files...
git log --all -- IPlugExamples/IPlugSideChain/IPlugSideChain_Controls.h
> prints list of all commits...
Using the first listed commit:
git checkout 93350c42ae141eae60287c20ccdd32e569d13234~1 IPlugExamples/IPlugSideChain/IPlugSideChain_Controls.h