Remove calls to deprecated MessageLoop methods in base.

base/files/important_file_writer_unittest.cc

Index: base/files/important_file_writer_unittest.cc
diff --git a/base/files/important_file_writer_unittest.cc b/base/files/important_file_writer_unittest.cc
index ba1d4d3f9324e74de2066432d3ddeb5344be90a2..43e051ebcfadf108e3a244420c5a01d5397396a9 100644
--- a/base/files/important_file_writer_unittest.cc
+++ b/base/files/important_file_writer_unittest.cc
@@ -157,7 +157,7 @@ TEST_F(ImportantFileWriterTest, ScheduleWrite) {
   ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, MessageLoop::QuitWhenIdleClosure(),
       TimeDelta::FromMilliseconds(100));
-  MessageLoop::current()->Run();
+  RunLoop().Run();
   EXPECT_FALSE(writer.HasPendingWrite());
   ASSERT_TRUE(PathExists(writer.path()));
   EXPECT_EQ("foo", GetFileContent(writer.path()));
@@ -173,7 +173,7 @@ TEST_F(ImportantFileWriterTest, DoScheduledWrite) {
   ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, MessageLoop::QuitWhenIdleClosure(),
       TimeDelta::FromMilliseconds(100));
-  MessageLoop::current()->Run();
+  RunLoop().Run();
   EXPECT_FALSE(writer.HasPendingWrite());
   ASSERT_TRUE(PathExists(writer.path()));
   EXPECT_EQ("foo", GetFileContent(writer.path()));
@@ -190,7 +190,7 @@ TEST_F(ImportantFileWriterTest, BatchingWrites) {
   ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, MessageLoop::QuitWhenIdleClosure(),
       TimeDelta::FromMilliseconds(100));
-  MessageLoop::current()->Run();
+  RunLoop().Run();
   ASSERT_TRUE(PathExists(writer.path()));
   EXPECT_EQ("baz", GetFileContent(writer.path()));
 }