Merge branch '3.4' into 4.4

* 3.4:
  Added documentation for __toString feature in StopWatch event

Author: javiereguiluz

components/stopwatch.rst

@@ -27,10 +27,15 @@ time of certain parts of code so that you don't constantly have to parse
     use Symfony\Component\Stopwatch\Stopwatch;
 
     $stopwatch = new Stopwatch();
+
     // starts event named 'eventName'
     $stopwatch->start('eventName');
-    // ... some code goes here
+
+    // ... run your code here
+
     $event = $stopwatch->stop('eventName');
+    // you can convert $event into a string for a quick summary
+    // e.g. (string) $event = '4.50 MiB - 26 ms'
 
 The :class:`Symfony\\Component\\Stopwatch\\StopwatchEvent` object can be retrieved
 from the  :method:`Symfony\\Component\\Stopwatch\\Stopwatch::start`,