This is a reland of 15fe64c0
Original change's description:
> [wasm] Handle non-asm-js case in WasmCompiledModule::GetAsmJsSourcePosition.
> 
> This hides more implementation details and simplifies callers.
> 
> R=ahaas@chromium.org
> 
> Bug: 
> Change-Id: I4809611c55b810a3b0674713e12f3f17401e6c9c
> Reviewed-on: https://chromium-review.googlesource.com/620713
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Commit-Queue: Ben Titzer <titzer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47434}

Change-Id: Ica097f43e5f9122eb44b537822f9021d5eab2703
Reviewed-on: https://chromium-review.googlesource.com/643207Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47716}