From f768afdd3104e7da663aa82e1e8f969aea3f85c3 Mon Sep 17 00:00:00 2001
From: Lei Zhang <thestig@chromium.org>
Date: Thu, 22 Aug 2019 11:44:27 -0700
Subject: [PATCH] Handle unsupported configs in CreatePrinterHandlerTaskRunner().

CreatePrinterHandlerTaskRunner(), which was added in
https://crrev.com/658397, used ifdefs to only handle the supported build
configs. Add a #else case as a catch-all to conservatively handle the
unsupported configs. Since it is only a couple lines of trivial code,
doing this does not create much of a maintenance burden.

(backported to chromium-76)

Bug: 990727
Change-Id: I07bd21abaeffc8223e88b519c3891185d5d2be12
---

diff --git a/chrome/browser/ui/webui/print_preview/local_printer_handler_default.cc b/chrome/browser/ui/webui/print_preview/local_printer_handler_default.cc
index 03bd08a..e9c6996 100644
--- a/chrome/browser/ui/webui/print_preview/local_printer_handler_default.cc
+++ b/chrome/browser/ui/webui/print_preview/local_printer_handler_default.cc
@@ -33,12 +33,15 @@ scoped_refptr<base::TaskRunner> CreatePrinterHandlerTaskRunner() {
   static constexpr base::TaskTraits kTraits = {
       base::MayBlock(), base::TaskPriority::USER_VISIBLE};

-#if defined(OS_WIN)
-  // Windows drivers are likely not thread-safe.
-  return base::CreateSingleThreadTaskRunnerWithTraits(kTraits);
-#elif defined(USE_CUPS)
+#if defined(USE_CUPS)
   // CUPS is thread safe.
   return base::CreateTaskRunnerWithTraits(kTraits);
+#elif defined(OS_WIN)
+  // Windows drivers are likely not thread-safe.
+  return base::CreateSingleThreadTaskRunnerWithTraits(kTraits);
+#else
+  // Be conservative on unsupported platforms.
+  return base::CreateSingleThreadTaskRunnerWithTraits(kTraits);
 #endif
 }