Use ScopedTaskEnvironment instead of MessageLoop in tests that use v8.

extensions/renderer/gc_callback_unittest.cc

Index: extensions/renderer/gc_callback_unittest.cc
diff --git a/extensions/renderer/gc_callback_unittest.cc b/extensions/renderer/gc_callback_unittest.cc
index 483f134dbec2361eeb1047c390c83fcb9d47e6b6..c03270d3c60c808bd647fe91822bb6b456bcb5ef 100644
--- a/extensions/renderer/gc_callback_unittest.cc
+++ b/extensions/renderer/gc_callback_unittest.cc
@@ -2,15 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "extensions/renderer/gc_callback.h"
+
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
 #include "extensions/common/features/feature.h"
-#include "extensions/renderer/gc_callback.h"
 #include "extensions/renderer/scoped_web_frame.h"
 #include "extensions/renderer/script_context.h"
 #include "extensions/renderer/script_context_set.h"
@@ -34,8 +35,6 @@ class GCCallbackTest : public testing::Test {
   GCCallbackTest() : script_context_set_(&active_extensions_) {}
 
  protected:
-  base::MessageLoop& message_loop() { return message_loop_; }
-
   ScriptContextSet& script_context_set() { return script_context_set_; }
 
   v8::Local<v8::Context> v8_context() {
@@ -71,7 +70,8 @@ class GCCallbackTest : public testing::Test {
     RequestGarbageCollection();
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
+
   ScopedWebFrame web_frame_;  // (this will construct the v8::Isolate)
   // ExtensionsRendererClient is a dependency of ScriptContextSet.
   TestExtensionsRendererClient extensions_renderer_client_;