Foozie came up with a mind-boggling example hitting a similarly
mind-boggling bug: object construction (JSObject::New) wants to create
the constructor's function initial map (JSFunction::GetDerivedMap ->
JSFunction::EnsureHasInitialMap). To do so, it calls
JSFunction::CalculateExpectedNofProperties. This harmless sounding
function triggers compilation of the function. Since we're running with
--always-opt, this is an optimizing compilation. Turbofan ends up
depending on the function's "prototype" property, for which it wants to
create the initial map so that it can install the code dependency. That
is, EnsureHasInitialMap is reentered. At this point there is no further
compilation attempt because the bytecode now exists. The initial map is
created and installed on the function, and TF records the code
dependency on that map. When CalculateExpectedNofProperties returns
control to the outer EnsureHasInitialMap, yet another initial map is
created and set on the function, forgetting the previous one and thus
the code dependency.

I'm not sure if this bug can only be observed with --always-opt. The fix
is general.

Bug: chromium:1092011
Change-Id: I8b972748e49b9eb8f06fa17ea9ca037de2bd7532
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2238570Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68292}