This adds a decorator to add the wasm bytecode offset as origin
for graph nodes and emits a little table that maps lines in the
generated wasm assembly listing to the corresponding bytecode
offset.

Change-Id: Ibc0431a122e543f95173ffc3b1b4ca461e372f28
Reviewed-on: https://chromium-review.googlesource.com/1071290Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53484}