Bug 1573184 - Update comments in TestAudioCallbackDriver. r=jya

Differential Revision: https://phabricator.services.mozilla.com/D41576

--HG--
extra : moz-landing-system : lando

dom/media/gtest/TestAudioCallbackDriver.cpp

@@ -53,14 +53,14 @@ TEST(TestAudioCallbackDriver, Revive)
   EXPECT_TRUE(driver->ThreadRunning()) << "Verify thread is running";
   EXPECT_TRUE(driver->IsStarted()) << "Verify thread is started";
 
-  // This will block untill all events has been executed.
+  // This will block untill all events have been executed.
   driver->AsAudioCallbackDriver()->Shutdown();
   EXPECT_FALSE(driver->ThreadRunning()) << "Verify thread is not running";
   EXPECT_FALSE(driver->IsStarted()) << "Verify thread is not started";
 
   // This is required because the MSG and the driver hold references between
-  // each other. The driver has a reference to SharedThreadPool which would
-  // block for ever if it was not cleared. The same logic exists in
+  // each other. The driver has a reference to SharedThreadPool which will
+  // block for ever if it is not cleared. The same logic exists in
   // MediaStreamGraphShutDownRunnable
   graph->mDriver = nullptr;
 }