[AST] Get the ObjC accessor name, not the one parsed from Swift.

Fixes rdar://problem/55519276.

Author: varungandhi-apple

lib/AST/Decl.cpp

@@ -4930,7 +4930,7 @@ getNameFromObjcAttribute(const ObjCAttr *attr, DeclName preferredName) {
 ObjCSelector
 AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
   // If the getter has an @objc attribute with a name, use that.
-  if (auto getter = getParsedAccessor(AccessorKind::Get)) {
+  if (auto getter = getAccessor(AccessorKind::Get)) {
       if (auto name = getNameFromObjcAttribute(getter->getAttrs().
           getAttribute<ObjCAttr>(), preferredName))
         return *name;
@@ -4960,7 +4960,7 @@ AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
 ObjCSelector
 AbstractStorageDecl::getObjCSetterSelector(Identifier preferredName) const {
   // If the setter has an @objc attribute with a name, use that.
-  auto setter = getParsedAccessor(AccessorKind::Set);
+  auto setter = getAccessor(AccessorKind::Set);
   auto objcAttr = setter ? setter->getAttrs().getAttribute<ObjCAttr>()
                          : nullptr;
   if (auto name = getNameFromObjcAttribute(objcAttr, DeclName(preferredName))) {

test/PrintAsObjC/getter_setter.swift

@@ -12,15 +12,14 @@ import Foundation
 // written in Objective-C.
 public final class Saiyan: NSObject, PowerProtocol {
   public var level: Int64
-  // FIXME: The getter and setter names should show up here.
-  // HEADER: @property (nonatomic) int64_t level;
+  // HEADER: @property (nonatomic, getter=getPower, setter=setPower:) int64_t level;
   // IRCHECK1: METACLASS_DATA__TtC13getter_setter6Saiyan
-  // IRCHECK1-NOT: selector_data(getPower)
-  // IRCHECK1-NOT: selector_data(setPower:)
+  // IRCHECK1: selector_data(getPower)
+  // IRCHECK1: selector_data(setPower:)
   // IRCHECK1: INSTANCE_METHODS__TtC13getter_setter6Saiyan
   // IRCHECK2: METACLASS_DATA__TtC13getter_setter6Saiyan
-  // IRCHECK2: selector_data(level)
-  // IRCHECK2: selector_data(setLevel:)
+  // IRCHECK2-NOT: selector_data(level)
+  // IRCHECK2-NOT: selector_data(setLevel:)
   // IRCHECK2: INSTANCE_METHODS__TtC13getter_setter6Saiyan
   public override init() {
     level = 9001