Replace vector<SwitchCase> in Switch with a StatementArray.

This is conceptually the same thing, but we have various places in the
code which expect a unique_ptr<Statement>, and they don't allow a
unique_ptr<SwitchCase> to be passed in, since the types don't match.

This change is particularly relevant to the ProgramWriter, which will be
updated in a followup CL to pass the unique_ptr to visit methods.

Change-Id: I012669fa429a13658ac2be31342c92750fe84b92
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/382723
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
10 files changed