Use modern base APIs to avoid base::MessageLoop::current() calls in /chrome/browser/printing

This is a precusor cleanup extracted from
https://chromium-review.googlesource.com/c/chromium/src/+/957760/7
in the broader effort to restrict usage of MessageLoop::current().

This CL was uploaded by git cl split.

R=dpapad@chromium.org

Bug: 825327
Change-Id: Ibbd7b8f1c59f8e1022b9d77dfcc4cf6e8490a24e
Reviewed-on: https://chromium-review.googlesource.com/986747
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548332}

chrome/browser/printing/print_job.cc

@@ -41,11 +41,7 @@ void HoldRefCallback(scoped_refptr<PrintJobWorkerOwner> owner,
 
 PrintJob::PrintJob()
     : is_job_pending_(false), is_canceling_(false), quit_factory_(this) {
-  // This is normally a UI message loop, but in unit tests, the message loop is
-  // of the 'default' type.
-  DCHECK(base::MessageLoopForUI::IsCurrent() ||
-         base::MessageLoop::current()->type() ==
-             base::MessageLoop::TYPE_DEFAULT);
+  DCHECK(base::MessageLoopForUI::IsCurrent());
 }
 
 PrintJob::~PrintJob() {

chrome/browser/printing/print_job_unittest.cc

@@ -9,7 +9,6 @@
 #include <vector>
 
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
@@ -91,12 +90,11 @@ TEST(PrintJobTest, SimplePrint) {
   // Test the multi-threaded nature of PrintJob to make sure we can use it with
   // known lifetime.
 
-  content::TestBrowserThreadBundle thread_bundle_;
-  content::NotificationRegistrar registrar_;
+  content::TestBrowserThreadBundle thread_bundle;
+  content::NotificationRegistrar registrar;
   TestPrintNotificationObserver observer;
-  registrar_.Add(&observer,
-                 content::NOTIFICATION_ALL,
-                 content::NotificationService::AllSources());
+  registrar.Add(&observer, content::NOTIFICATION_ALL,
+                content::NotificationService::AllSources());
   volatile bool check = false;
   scoped_refptr<PrintJob> job(new TestPrintJob(&check));
   EXPECT_TRUE(job->RunsTasksInCurrentSequence());
@@ -116,7 +114,7 @@ TEST(PrintJobTest, SimplePrint) {
 
 TEST(PrintJobTest, SimplePrintLateInit) {
   volatile bool check = false;
-  base::MessageLoop current;
+  content::TestBrowserThreadBundle thread_bundle;
   scoped_refptr<PrintJob> job(new TestPrintJob(&check));
   job = nullptr;
   EXPECT_TRUE(check);