This CL allows selection/highlighting of wasm source when a graph node
is clicked.

Bug: v8:7327
Change-Id: I4a3347a83c8a38804feabffefaefd761596005c3
Reviewed-on: https://chromium-review.googlesource.com/1092712
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53636}