Remove calls to deprecated MessageLoop methods in media.

media/base/serial_runner_unittest.cc

Index: media/base/serial_runner_unittest.cc
diff --git a/media/base/serial_runner_unittest.cc b/media/base/serial_runner_unittest.cc
index 236dc776591658b099593693911db30a23474012..800046a631bd466200543c38f9b6726a35248325 100644
--- a/media/base/serial_runner_unittest.cc
+++ b/media/base/serial_runner_unittest.cc
@@ -9,6 +9,8 @@
 #include "base/debug/stack_trace.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/serial_runner.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -22,10 +24,10 @@ class SerialRunnerTest : public ::testing::Test {
   ~SerialRunnerTest() override {}
 
   void RunSerialRunner() {
-    message_loop_.PostTask(FROM_HERE, base::Bind(
-        &SerialRunnerTest::StartRunnerInternal, base::Unretained(this),
-        bound_fns_));
-    message_loop_.RunUntilIdle();
+    message_loop_.task_runner()->PostTask(
+        FROM_HERE, base::Bind(&SerialRunnerTest::StartRunnerInternal,
+                              base::Unretained(this), bound_fns_));
+    base::RunLoop().RunUntilIdle();
   }
 
   // Pushes a bound function to the queue that will run its callback with
@@ -118,8 +120,9 @@ class SerialRunnerTest : public ::testing::Test {
 
   void CancelSerialRunner(const PipelineStatusCB& status_cb) {
     // Tasks run by |runner_| shouldn't reset it, hence we post a task to do so.
-    message_loop_.PostTask(FROM_HERE, base::Bind(
-        &SerialRunnerTest::ResetSerialRunner, base::Unretained(this)));
+    message_loop_.task_runner()->PostTask(
+        FROM_HERE, base::Bind(&SerialRunnerTest::ResetSerialRunner,
+                              base::Unretained(this)));
     status_cb.Run(PIPELINE_OK);
   }