Use ScopedTaskEnvironment instead of MessageLoopForUI in content tests.

content/browser/renderer_host/input/input_router_impl_perftest.cc

Index: content/browser/renderer_host/input/input_router_impl_perftest.cc
diff --git a/content/browser/renderer_host/input/input_router_impl_perftest.cc b/content/browser/renderer_host/input/input_router_impl_perftest.cc
index 42f4415fa91895738a12c344da45e1fff1dbea2d..a677f3291c858c00f9b9f7a1735012c56561a614 100644
--- a/content/browser/renderer_host/input/input_router_impl_perftest.cc
+++ b/content/browser/renderer_host/input/input_router_impl_perftest.cc
@@ -9,6 +9,7 @@
 
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "content/browser/renderer_host/input/input_ack_handler.h"
 #include "content/browser/renderer_host/input/input_router_client.h"
 #include "content/browser/renderer_host/input/input_router_impl.h"
@@ -217,7 +218,10 @@ bool ShouldBlockEventStream(const blink::WebInputEvent& event) {
 
 class InputRouterImplPerfTest : public testing::Test {
  public:
-  InputRouterImplPerfTest() : last_input_id_(0) {}
+  InputRouterImplPerfTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        last_input_id_(0) {}
   ~InputRouterImplPerfTest() override {}
 
  protected:
@@ -348,12 +352,12 @@ class InputRouterImplPerfTest : public testing::Test {
   }
 
  private:
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   int64_t last_input_id_;
   std::unique_ptr<NullIPCSender> sender_;
   std::unique_ptr<NullInputRouterClient> client_;
   std::unique_ptr<NullInputAckHandler> ack_handler_;
   std::unique_ptr<InputRouterImpl> input_router_;
-  base::MessageLoopForUI message_loop_;
 };
 
 const size_t kDefaultSteps(100);