Remove fRootSymbolTable from IR Generator

Two Compiler methods that use the root symbol table are still dangerous,
they're polluting the global namespace. For long-lived compilers, we
don't want to do that. takeOwnership is only used in tests, but
registerExternalValue is used by particles. Thinking I'll move that to
an optional argument to convertProgram, or a field on Settings.

Change-Id: Ic88d29d053510001931dcc2388aba2dc83a953ea
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/319030
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
3 files changed