... instead of getting it from the FunctionMirror. For WASM frames
(including asm.js -> WASM), the function is either unresolved or does
not contain the script.

The added test case failed before this CL.

R=kozyatinskiy@chromium.org, yangguo@chromium.org, titzer@chromium.org
BUG=v8:4203

Review-Url: https://codereview.chromium.org/2415073003
Cr-Commit-Position: refs/heads/master@{#40348}