Convert printer status query check to switch statement

Using a switch statement better represents the fact that the
PrinterQueryResult enum only contains 3 possible options: SUCCESS,
UNREACHABLE, or UNKNOWN_FAILURE.

Bug: 1059607
Change-Id: I0887d532a9f2bc67f63ba218401480ae7e7b8762
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2349986
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797099}

chrome/browser/chromeos/printing/cups_printers_manager.cc

@@ -400,7 +400,8 @@ class CupsPrintersManagerImpl
                          PrinterStatusCallback cb,
                          PrinterQueryResult result,
                          const ::printing::PrinterStatus& printer_status) {
-    if (result == PrinterQueryResult::UNREACHABLE) {
+    switch (result) {
+      case PrinterQueryResult::UNREACHABLE: {
         PRINTER_LOG(ERROR)
             << "Printer status request failed. Could not reach printer "
             << printer_id;
@@ -410,10 +411,9 @@ class CupsPrintersManagerImpl
                 kPrinterUnreachable,
             CupsPrinterStatus::CupsPrinterStatusReason::Severity::kError);
         std::move(cb).Run(std::move(error_printer_status));
-      return;
+        break;
       }
-
-    if (result == PrinterQueryResult::UNKNOWN_FAILURE) {
+      case PrinterQueryResult::UNKNOWN_FAILURE: {
         PRINTER_LOG(ERROR) << "Printer status request failed. Unknown failure "
                               "trying to reach printer "
                            << printer_id;
@@ -422,21 +422,25 @@ class CupsPrintersManagerImpl
             CupsPrinterStatus::CupsPrinterStatusReason::Reason::kUnknownReason,
             CupsPrinterStatus::CupsPrinterStatusReason::Severity::kWarning);
         std::move(cb).Run(std::move(error_printer_status));
-      return;
+        break;
       }
-
-    if (result == PrinterQueryResult::SUCCESS) {
+      case PrinterQueryResult::SUCCESS: {
         // Convert printing::PrinterStatus to printing::CupsPrinterStatus
         CupsPrinterStatus cups_printers_status =
             PrinterStatusToCupsPrinterStatus(printer_id, printer_status);
 
-      // Save the PrinterStatus so it can be attached along side future Printer
-      // retrievals.
+        // Save the PrinterStatus so it can be attached along side future
+        // Printer retrievals.
         printers_.SavePrinterStatus(printer_id, cups_printers_status);
 
         // Send status back to the handler through PrinterStatusCallback.
         std::move(cb).Run(std::move(cups_printers_status));
-      return;
+        break;
+      }
+      default: {
+        NOTREACHED();
+        break;
+      }
     }
   }