Visit label blocks in try statements during declaration

This problem was discovered by mvstanton@'s forEach Torque patch. In the absense
of test coverage for Torque, his patch will serve as the regression test case
for this bug when it lands.

Change-Id: Ic77446a8e46168928da221e6eb18753dd6478c87
Reviewed-on: https://chromium-review.googlesource.com/1018763Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52688}

src/torque/declaration-visitor.cc

@@ -202,6 +202,10 @@ void DeclarationVisitor::Visit(TryCatchStatement* stmt) {
   for (CatchBlock* block : stmt->catch_blocks) {
     Visit(block->body);
   }
+
+  for (LabelBlock* block : stmt->label_blocks) {
+    Visit(block->body);
+  }
 }
 
 }  // namespace torque