Do not flush main thread tasks in ~ScopedTaskEnvironment.

base/test/scoped_task_environment.cc

Index: base/test/scoped_task_environment.cc
diff --git a/base/test/scoped_task_environment.cc b/base/test/scoped_task_environment.cc
index d1c0907c4b0d7e32ab411826fe006c98efc3a7d6..22ed28cd2c6f535b6049195583a1f7d1327ae3d3 100644
--- a/base/test/scoped_task_environment.cc
+++ b/base/test/scoped_task_environment.cc
@@ -55,8 +55,8 @@ ScopedTaskEnvironment::ScopedTaskEnvironment(MainThreadType main_thread_type)
 }
 
 ScopedTaskEnvironment::~ScopedTaskEnvironment() {
-  RunLoop().RunUntilIdle();
-
+  // Intentionally do not RunLoop().RunUntilIdle() here as this simulates the
+  // replaced base::~MessageLoop() behaviour better.
   DCHECK_EQ(TaskScheduler::GetInstance(), task_scheduler_);
   // Without FlushForTesting(), DeleteSoon() and ReleaseSoon() tasks could be
   // skipped, resulting in memory leaks.