We need to create one {WasmCompiledModule} before creating the
{WasmModuleObject}. This CL refactors the code such that the
{WasmModuleObject} itself creates the {WasmCompiledModule}. This moves
us closer to removing the {WasmCompiledModule}.

R=titzer@chromium.org

Change-Id: I9f85e47f643c39840036f4f1f92df736732c8f74
Reviewed-on: https://chromium-review.googlesource.com/1105762Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53833}