This CL enables source maps support for wasm. Devtools should
be able to pick up source_mapping_url parsed here and load the
corresponding source maps.

R=kozyatinskiy@chromium.org,clemensh@chromium.org,titzer@chromium.org,yangguo@chromium.org
BUG=v8:8081

Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;luci.chromium.try:linux_chromium_rel_ng;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I1db0ff597d229e7db8d383fe9ee081c7fa4e7648
Reviewed-on: https://chromium-review.googlesource.com/1185973
Commit-Queue: Aseem Garg <aseemgarg@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55878}