Merge branch '5.1' into 5.2

* 5.1:
  Use ::class keyword when possible

Author: fabpot

Tests/Controller/ArgumentResolverTest.php

@@ -132,7 +132,7 @@ public function testGetArgumentsFailsOnUnresolvedValue()
             self::$resolver->getArguments($request, $controller);
             $this->fail('->getArguments() throws a \RuntimeException exception if it cannot determine the argument value');
         } catch (\Exception $e) {
-            $this->assertInstanceOf('\RuntimeException', $e, '->getArguments() throws a \RuntimeException exception if it cannot determine the argument value');
+            $this->assertInstanceOf(\RuntimeException::class, $e, '->getArguments() throws a \RuntimeException exception if it cannot determine the argument value');
         }
     }