This removes duplicate storage of edges in the graph view, thereby
reducing memory overhead.

Bug: v8:7327
Notry: true
Change-Id: I70df4bc102add8c89bc5145f01c0555b3e0a73d7
Reviewed-on: https://chromium-review.googlesource.com/c/1396085
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58548}