The asm-wasm-builder started allocating SharedFunctionInfos,
this makes it bad we'd passed Script by pointer (due to ignorance).
Switching to Handle<Script>.

R=clemensh@chromium.org,titzer@chromium.org
BUG=v8:5716

Review-Url: https://codereview.chromium.org/2552873003
Cr-Commit-Position: refs/heads/master@{#41529}