Use ScopedTaskEnvironment instead of MessageLoopForUI in chrome tests.

chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc

Index: chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc
diff --git a/chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc b/chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc
index 87c653dc791dfa08ced44626750d3ddc2b7ffd51..dc7769b45594f0a8b5c3eaed4e3da3d00d3077cc 100644
--- a/chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc
+++ b/chrome/browser/extensions/api/image_writer_private/image_writer_private_apitest.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "chrome/browser/extensions/api/image_writer_private/operation.h"
@@ -19,6 +19,10 @@ using extensions::image_writer::FakeImageWriterClient;
 
 class ImageWriterPrivateApiTest : public ExtensionApiTest {
  public:
+  ImageWriterPrivateApiTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
+
   void SetUpInProcessBrowserTestFixture() override {
     ExtensionApiTest::SetUpInProcessBrowserTestFixture();
     test_utils_.SetUp(true);
@@ -89,7 +93,7 @@ class ImageWriterPrivateApiTest : public ExtensionApiTest {
 #endif
 
  protected:
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   image_writer::ImageWriterTestUtils test_utils_;
 };