Merge branch '4.3' into 4.4

* 4.3:
  [HttpKernel] fixed class having a leading \ in a route controller
  [HttpKernel] trim the leading backslash in the controller init

src/Symfony/Component/HttpKernel/Controller/ContainerControllerResolver.php

@@ -47,6 +47,8 @@ class ContainerControllerResolver extends ControllerResolver
      */
     protected function instantiateController($class)
     {
+        $class = ltrim($class, '\\');
+
         if ($this->container->has($class)) {
             return $this->container->get($class);
         }

src/Symfony/Component/HttpKernel/Tests/Controller/ContainerControllerResolverTest.php

@@ -119,6 +119,36 @@ class ContainerControllerResolverTest extends ControllerResolverTest
         $this->assertSame($service, $controller);
     }
 
+    /**
+     * @dataProvider getControllers
+     */
+    public function testInstantiateControllerWhenControllerStartsWithABackslash($controller)
+    {
+        $service = new ControllerTestService('foo');
+        $class = ControllerTestService::class;
+
+        $container = $this->createMockContainer();
+        $container->expects($this->once())->method('has')->with($class)->willReturn(true);
+        $container->expects($this->once())->method('get')->with($class)->willReturn($service);
+
+        $resolver = $this->createControllerResolver(null, $container);
+        $request = Request::create('/');
+        $request->attributes->set('_controller', $controller);
+
+        $controller = $resolver->getController($request);
+
+        $this->assertInstanceOf(ControllerTestService::class, $controller[0]);
+        $this->assertSame('action', $controller[1]);
+    }
+
+    public function getControllers()
+    {
+        return [
+            ['\\'.ControllerTestService::class.'::action'],
+            ['\\'.ControllerTestService::class.':action'],
+        ];
+    }
+
     public function testExceptionWhenUsingRemovedControllerServiceWithClassNameAsName()
     {
         $this->expectException('InvalidArgumentException');