Reapply "Rename mappedBy to map."
Reapply "Rename mappedBy to map."

This reverts commit r17907.

TBR.

Review URL: https://codereview.chromium.org//12090093

git-svn-id: a0fc6a377c96b9059f80895148836233a16d98be@17918 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/http,dart-lang/http,dart-lang/http,kasperpeulen/http,dart-lang/http,dart-lang/http,dart-lang/http,dart-lang/http,dart-lang/http,donny-dont/http