When a wasm function has a large stack frame, the x64 code generator
performs the stack overflow check before constructing the frame. This
requires using the `address_of_real_stack_limit` external reference, as
well as the `ThrowWasmStackOverflow` runtime function.

`ThrowWasmStackOverflow` is called via a generated trampoline, but it is
not a builtin, so the serializer adds it to the `stub_lookup_` map. This
map is encoded by using a monotonically increasing `stub_id` that starts
at 0.

When the function is serialized, a stub is differentiated from a builtin
by which half of the `i32` bits is used, upper or lower. A stub only
uses the lower 16 bits and a builtin only uses the upper 16 bits.

The deserializer checks whether the lower 16 bits are 0; if so, it is
determined to be a builtin. But if the `stub_id` is 0, then it will be
confused with builtin 0 (`RecordWrite`). Calling the builtin instead of
the stub causes a crash.

This CL starts all `stub_id`s at 1, which prevents the builtin/stub
confusion.

There is an additional bug that is not fixed by this CL:
`ThrowWasmStackOverflow` shouldn't be called at all. Currently it is
called because `address_of_real_stack_limit` is a thread-local value
that is not properly relocated.

Bug: chromium:808848
Change-Id: I06b3e650ea58ad717dcc47a3716443e16582e711
Reviewed-on: https://chromium-review.googlesource.com/981687Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ben Smith <binji@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52252}