Fixes getImageData(100) calling itself endlessly (introduced via
https://github.com/eclipse-platform/eclipse.platform.ui/commit/c2fe1447c499d0de02b24e5bd07e18d559105e0e
) by reintroducing the bigger getImageData(100) and getImageData()
endlessly (introduced in 2017 via
https://github.com/eclipse-platform/eclipse.platform.ui/commit/e6d12ca0ae4762273680dc65ae8eb6f211778acc
) that wasn't experienced thanks to the *happy accident* that it was
asbtract method and all implementations before that had their own and
every implementor since then most likely figured the endless loop while
developing.
Enhanced documentation to mention that.