Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/renderer/input/input_event_filter_unittest.cc

Index: content/renderer/input/input_event_filter_unittest.cc
diff --git a/content/renderer/input/input_event_filter_unittest.cc b/content/renderer/input/input_event_filter_unittest.cc
index c1876c6022d895749feafb6c39ed9fd8a3081182..b0c7e6784b36a432df6cbd9175c0db50eb4a21b1 100644
--- a/content/renderer/input/input_event_filter_unittest.cc
+++ b/content/renderer/input/input_event_filter_unittest.cc
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
@@ -193,7 +194,7 @@ class InputEventFilterTest : public testing::Test {
   }
 
  protected:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   scoped_refptr<base::TestSimpleTaskRunner> main_task_runner_;
 
   // Used to record IPCs sent by the filter to the RenderWidgetHost.