I introduced a new flag, --wasm-parallel-compilation, which turns on
parallel compilation of wasm modules. If parallel compilation is turned
on, then the compilation of wasm functions is split into three phases,
initialization, execution, and finalization. The execution phase is the
phase which is going to contain all the code that can be executed in
parallel. At the moment the execution phase is still empty.

R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/1928933002
Cr-Commit-Position: refs/heads/master@{#35875}