This moves the generation of the WasmCode structure into the
PipelineWasmCompilationJob, removing WasmCodeDesc in the process.
WasmCodeDesc was a structure that was not understood by other parts of
the compiler, including the disassembler. Using WasmCode right away
enables printing code comments for turbolizer.

Change-Id: Ie5cca131829bc842c51c999ea14d0dc339b3e028
Reviewed-on: https://chromium-review.googlesource.com/1073312
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53490}