Use ScopedTaskEnvironment instead of MessageLoop in tests that use v8.

gin/modules/timer_unittest.cc

Index: gin/modules/timer_unittest.cc
diff --git a/gin/modules/timer_unittest.cc b/gin/modules/timer_unittest.cc
index bd4b3450f0ac3c3caf71408f8d8055200326a445..665ea4e788d56bebf4170217433b20ce9349cab0 100644
--- a/gin/modules/timer_unittest.cc
+++ b/gin/modules/timer_unittest.cc
@@ -67,12 +67,6 @@ struct TestHelper {
                           result->GetWrapper(isolate).ToLocalChecked());
   }
 
-  void QuitSoon(base::MessageLoop* message_loop) {
-    message_loop->task_runner()->PostDelayedTask(
-        FROM_HERE, base::MessageLoop::QuitWhenIdleClosure(),
-        base::TimeDelta::FromMilliseconds(0));
-  }
-
   ShellRunnerDelegate delegate;
   std::unique_ptr<ShellRunner> runner;
   Runner::Scope scope;
@@ -94,8 +88,7 @@ TEST_F(TimerUnittest, OneShot) {
   helper.runner->Run(source, "script");
   EXPECT_EQ(0, helper.result->count());
 
-  helper.QuitSoon(&message_loop_);
-  base::RunLoop().Run();
+  base::RunLoop().RunUntilIdle();
   EXPECT_EQ(1, helper.result->count());
 }
 
@@ -110,8 +103,7 @@ TEST_F(TimerUnittest, OneShotCancel) {
   helper.runner->Run(source, "script");
   EXPECT_EQ(0, helper.result->count());
 
-  helper.QuitSoon(&message_loop_);
-  base::RunLoop().Run();
+  base::RunLoop().RunUntilIdle();
   EXPECT_EQ(0, helper.result->count());
 }
 
@@ -121,12 +113,15 @@ TEST_F(TimerUnittest, Repeating) {
   // TODO(aa): Cannot do: if (++result.count == 3) because of v8 bug. Create
   // test case and report.
   std::string source =
-     "timer.createRepeating(0, function() {"
-     "  result.count++;"
-     "  if (result.count == 3) {"
-     "    result.quit();"
-     "  }"
-     "});";
+      "var t = timer.createRepeating(0, function() {"
+      "  result.count++;"
+      "  if (result.count == 3) {"
+      "    /* Cancel the timer to prevent a hang when ScopedTaskEnvironment "
+      "       flushes main thread tasks. */"
+      "    t.cancel();"
+      "    result.quit();"
+      "  }"
+      "});";
 
   helper.runner->Run(source, "script");
   EXPECT_EQ(0, helper.result->count());
@@ -146,9 +141,8 @@ TEST_F(TimerUnittest, TimerCallbackToDestroyedRunner) {
   EXPECT_EQ(0, helper.result->count());
 
   // Destroy runner, which should destroy the timer object we created.
-  helper.QuitSoon(&message_loop_);
   helper.runner.reset(NULL);
-  base::RunLoop().Run();
+  base::RunLoop().RunUntilIdle();
 
   // Timer should not have run because it was deleted.
   EXPECT_EQ(0, helper.result->count());