... because we want to use BreakLocation also for wasm, but we don't
instantiate a DebugInfo for wasm.

R=yangguo@chromium.org, titzer@chromium.org
BUG=v8:5822

Review-Url: https://codereview.chromium.org/2621953002
Cr-Commit-Position: refs/heads/master@{#42283}