java_library allows .srcjars to be passed in srcs, which will be unzipped and all of their sources included in compilation. There is no equivalent for cc_library or other languages. This would be extremely useful to support genrules that create sets of source files that might not be fully defined at analysis time. See https://groups.google.com/forum/#!topic/bazel-discuss/O0MwYZLBaKU for more discussion.

It looks to me like the change would have to be made around CcCommon.java:254. The code to deal with source jars in Java is at AbstractLibraryBuilder.java:209