If you make use of javax.inject in your plugin and relied on org.eclipse.core.runtime reexporting it now you'll have to add import package for it explicitly. 
Bundle javax.inject was always optional import in org.eclipse.core.runtime thus it was never really promised to be there for clients. Combined with the fact that API can change underneath us  it made no sense to continue relying on this uncertain and even questionable structure "reexport optional dependency".
All clients affected from this have to explicitly Import-Package: javax.inject and thus ensure that it's properly resolved fot them.
Red Hat Eclipse Team