Fix for fuzzer-discovered use-after-free.

The inliner discovered that when a binary expression is inlined, its
type is not cloned into the destination's SymbolTable. This meant that
when the inlined-from function was later dead-stripped, the type pointer
would become dangling. Did a quick pass over inlineExpression and
inlineStatement and ensured that types are always copied.

Also found that `copy_if_needed` was making a copy of eligible types
each time one was encountered, instead of making one copy and reusing
it. This is fixed as well.

Change-Id: Iee3259ab038dfb04034bf0110af1909ccffec3de
Bug: oss-fuzz:29444
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/354219
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
7 files changed