For the asm.js to WASM pipeline, the current stack traces only show
low-level WASM information.
This CL maps this back to asm.js source positions.
It does so by attaching the asm.js source Script to the compiled WASM
module, and emitting a delta-encoded table which maps from WASM byte
offsets to positions within that Script. As asm.js code does not throw
exceptions, we only store a mapping for call instructions.

The new AsmJsWasmStackFrame implementation inherits from
WasmStackFrame, but contains the logic to provide the source script and
the position inside of it.
What is still missing is the JSFunction object returned by
CallSite.getFunction(). We currently return null.

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

Review-Url: https://codereview.chromium.org/2404253002
Cr-Commit-Position: refs/heads/master@{#40205}