Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/quota/mock_quota_manager_unittest.cc

Index: content/browser/quota/mock_quota_manager_unittest.cc
diff --git a/content/browser/quota/mock_quota_manager_unittest.cc b/content/browser/quota/mock_quota_manager_unittest.cc
index e71c3eed49de17911d7a2b8759368c2c9e4220c3..115b5e37ff6fa9b263f9e0c8559fcb7decef3abe 100644
--- a/content/browser/quota/mock_quota_manager_unittest.cc
+++ b/content/browser/quota/mock_quota_manager_unittest.cc
@@ -12,6 +12,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "content/public/test/mock_special_storage_policy.h"
 #include "content/public/test/mock_storage_client.h"
@@ -101,7 +102,7 @@ class MockQuotaManagerTest : public testing::Test {
   }
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::ScopedTempDir data_dir_;
   scoped_refptr<MockQuotaManager> manager_;
   scoped_refptr<MockSpecialStoragePolicy> policy_;