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This adds dashed links w/ arrows to the graph, indicating opener/openee
embedder/embeddee relationships. It also makes pinned nodes visually
distinct by changing their stroke color.

BUG=1085129

Change-Id: I0bd75a90c83a735b7d56ff2905d7d3d7b7be6e84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2227369
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774935}