Bump monolog to 1.19 and use the agent regex const from parent, see #22264

src/Symfony/Bridge/Monolog/Handler/ChromePhpHandler.php

@@ -41,7 +41,7 @@ class ChromePhpHandler extends BaseChromePhpHandler
             return;
         }
 
-        if (!preg_match('{\b(?:Chrome/\d+(?:\.\d+)*|Firefox/(?:4[3-9]|[5-9]\d|\d{3,})(?:\.\d)*)\b}', $event->getRequest()->headers->get('User-Agent'))) {
+        if (!preg_match(static::USER_AGENT_REGEX, $event->getRequest()->headers->get('User-Agent'))) {
             $this->sendHeaders = false;
             $this->headers = array();
 

src/Symfony/Bridge/Monolog/composer.json

@@ -17,7 +17,7 @@
     ],
     "require": {
         "php": ">=5.5.9",
-        "monolog/monolog": "~1.11",
+        "monolog/monolog": "~1.19",
         "symfony/http-kernel": "~2.8|~3.0"
     },
     "require-dev": {