process uses the same code as lib and decides at runtime which
code to run. Fix the debug build by making sure that all infrastructure
code is available in both process and lib by building common code
not shared directly through chromium sources in a separate static lib.

 * nothing is shown on the screen
 * content_shell.pak is required to be present in the example/ directory (copy from existing build)

We'll probably add a qmake wrapper for it later, but for now that should do.