Instead of computing the disassmebly and offset tables eagerly on
registering a WASM function with a debugger agent, only generate
it when the source or offset tables are actually required. This is
implemented using a lazy, memoizing supplier that is shared
between the debugger agent and wasm translator.

Bug: chromium:794941
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I1a2f7dd71ab65c80f91ddee4f7babbdf33d2e74b
Reviewed-on: https://chromium-review.googlesource.com/918641
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51762}