https://bugs.webkit.org/show_bug.cgi?id=124464

Source/JavaScriptCore: 

Reviewed by Sam Weinig.
        
All global variables that are candidates for watchpoint-based constant inference (i.e.
not 'const' variables) will now have WatchpointSet's associated with them and those
are used to drive the inference by tracking three states of each variable:
        
Uninitialized: the variable's value is Undefined and the WatchpointSet state is
    ClearWatchpoint.
        
Initialized: the variable's value was set to something (could even be explicitly set
    to Undefined) and the WatchpointSet state is IsWatching.
        
Invalidated: the variable's value was set to something else (could even be the same
    thing as before but the point is that a put operation did execute again) and the
    WatchpointSet is IsInvalidated.
        
If the compiler tries to compile a GetGlobalVar and the WatchpointSet state is
IsWatching, then the current value of the variable can be folded in pl...