Remove calls to deprecated MessageLoop methods in components/previews/.

This CL removes calls to MessageLoop::RunUntilIdle from
components/previews/.

BUG=616447

Review-Url: https://codereview.chromium.org/2348503002
Cr-Commit-Position: refs/heads/master@{#418921}

components/previews/previews_io_data_unittest.cc

@@ -9,6 +9,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "components/previews/previews_ui_service.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -71,7 +72,7 @@ TEST_F(PreviewsIODataTest, TestInitialization) {
       new TestPreviewsIOData(loop_.task_runner(), loop_.task_runner())));
   set_ui_service(
       base::WrapUnique(new PreviewsUIService(io_data(), loop_.task_runner())));
-  loop_.RunUntilIdle();
+  base::RunLoop().RunUntilIdle();
   // After the outstanding posted tasks have run, |io_data_| should be fully
   // initialized.
   EXPECT_TRUE(io_data()->initialized());

components/previews/previews_ui_service_unittest.cc

@@ -9,6 +9,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "components/previews/previews_io_data.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -74,7 +75,7 @@ TEST_F(PreviewsUIServiceTest, TestInitialization) {
       new PreviewsIOData(loop_.task_runner(), loop_.task_runner())));
   set_ui_service(base::WrapUnique(
       new TestPreviewsUIService(io_data(), loop_.task_runner())));
-  loop_.RunUntilIdle();
+  base::RunLoop().RunUntilIdle();
   // After the outstanding posted tasks have run, SetIOData should have been
   // called for |ui_service_|.
   EXPECT_TRUE(ui_service()->io_data_set());