In order to avoid having to reconstitute the entire element model when
deserializing a library summary, we'll need to be able to create element
handles for any elements referenced by the library. Since element
handles operate using a "location", and the "location" records
information about the compilation unit containing the element, this
means that the library summary needs to track which unit each referenced
element lives in (even though this information would otherwise not be
semantically relevant).
R=scheglov@google.com
Review URL: https://codereview.chromium.org/1468583002 .
Paul Berry
84c3cdb048