Show more accurate message in profiler when missing stopwatch

src/Symfony/Bundle/WebProfilerBundle/Resources/views/Collector/time.html.twig

@@ -95,7 +95,11 @@
 
     <h2>Execution timeline</h2>
 
-    {% if collector.events is empty %}
+    {% if not collector.isStopwatchInstalled() %}
+        <div class="empty">
+            <p>The Stopwatch component is not installed. If you want to see timing events, run: <code>composer require symfony/stopwatch</code>.</p>
+        </div>
+    {% elseif collector.events is empty %}
         <div class="empty">
             <p>No timing events have been recorded. Are you sure that debugging is enabled in the kernel?</p>
         </div>

src/Symfony/Bundle/WebProfilerBundle/composer.json

@@ -17,7 +17,7 @@
     ],
     "require": {
         "php": "^5.5.9|>=7.0.8",
-        "symfony/http-kernel": "~3.3|~4.0",
+        "symfony/http-kernel": "~3.4.25|^4.2.6",
         "symfony/polyfill-php70": "~1.0",
         "symfony/routing": "~2.8|~3.0|~4.0",
         "symfony/twig-bridge": "~2.8|~3.0|~4.0",

src/Symfony/Component/HttpKernel/DataCollector/TimeDataCollector.php

@@ -47,6 +47,7 @@ public function collect(Request $request, Response $response, \Exception $except
             'token' => $response->headers->get('X-Debug-Token'),
             'start_time' => $startTime * 1000,
             'events' => [],
+            'stopwatch_installed' => \class_exists(Stopwatch::class, false),
         ];
     }
 
@@ -139,6 +140,14 @@ public function getStartTime()
         return $this->data['start_time'];
     }
 
+    /**
+     * @return bool whether or not the stopwatch component is installed
+     */
+    public function isStopwatchInstalled()
+    {
+        return $this->data['stopwatch_installed'];
+    }
+
     /**
      * {@inheritdoc}
      */

src/Symfony/Component/HttpKernel/Tests/DataCollector/TimeDataCollectorTest.php

@@ -15,6 +15,7 @@
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\DataCollector\TimeDataCollector;
+use Symfony\Component\Stopwatch\Stopwatch;
 
 /**
  * @group time-sensitive
@@ -51,5 +52,6 @@ public function testCollect()
 
         $c->collect($request, new Response());
         $this->assertEquals(123456000, $c->getStartTime());
+        $this->assertSame(\class_exists(Stopwatch::class, false), $c->isStopwatchInstalled());
     }
 }