Make sure context menu items for SourceFrame aren't added twice
Make sure context menu items for SourceFrame aren't added twice

R=dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org

Bug: 1271163
Change-Id: I1d822045eefae66393678aa8e752096ec4309772
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3297829
Reviewed-by: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Commit-Queue: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend