[compiler] Move generator optimization heuristics.

This moves the decision whether to optimize generator or async functions
into the AstNumberingVisitor. Optimization heuristics that are based on
the function source should be encapsulated in this class.

R=neis@chromium.org

Review-Url: https://codereview.chromium.org/2065543002
Cr-Commit-Position: refs/heads/master@{#36924}

src/ast/ast-numbering.cc

@@ -579,6 +579,10 @@ bool AstNumberingVisitor::Renumber(FunctionLiteral* node) {
     DisableCrankshaft(kRestParameter);
   }
 
+  if (IsGeneratorFunction(node->kind()) || IsAsyncFunction(node->kind())) {
+    DisableOptimization(kGenerator);
+  }
+
   VisitDeclarations(scope->declarations());
   VisitStatements(node->body());
 

src/factory.cc

@@ -2085,12 +2085,6 @@ Handle<SharedFunctionInfo> Factory::NewSharedFunctionInfo(
   shared->set_num_literals(number_of_literals);
   if (IsGeneratorFunction(kind)) {
     shared->set_instance_class_name(isolate()->heap()->Generator_string());
-    shared->DisableOptimization(kGenerator);
-  }
-  if (IsAsyncFunction(kind)) {
-    // TODO(caitp): Enable optimization of async functions when they are enabled
-    // for generators functions.
-    shared->DisableOptimization(kGenerator);
   }
   return shared;
 }