Merge branch '3.4' into 4.3

* 3.4:
  [Filesystem] [Serializer] fixes English grammar typo
  [Monolog Bridge] Fixed accessing static property as non static.
  Improve Symfony description
  [Validator] Add Japanese translation
  Remove some unused methods parameters
  Avoid empty \"If-Modified-Since\" header in validation request
  [Validator] ConstraintValidatorTestCase: add missing return value to mocked validate method calls

Author: fabpot

Resources/translations/validators.ja.xlf

@@ -362,6 +362,10 @@
                 <source>This password has been leaked in a data breach, it must not be used. Please use another password.</source>
                 <target>このパスワードは漏洩している為使用できません。</target>
             </trans-unit>
+            <trans-unit id="94">
+                <source>This value should be between {{ min }} and {{ max }}.</source>
+                <target>{{ min }}以上{{ max }}以下でなければなりません。</target>
+            </trans-unit>
         </body>
     </file>
 </xliff>

Test/ConstraintValidatorTestCase.php

@@ -178,7 +178,8 @@ protected function expectValidateAt($i, $propertyPath, $value, $group)
             ->willReturn($validator);
         $validator->expects($this->at(2 * $i + 1))
             ->method('validate')
-            ->with($value, $this->logicalOr(null, [], $this->isInstanceOf('\Symfony\Component\Validator\Constraints\Valid')), $group);
+            ->with($value, $this->logicalOr(null, [], $this->isInstanceOf('\Symfony\Component\Validator\Constraints\Valid')), $group)
+            ->willReturn($validator);
     }
 
     protected function expectValidateValueAt($i, $propertyPath, $value, $constraints, $group = null)
@@ -190,7 +191,8 @@ protected function expectValidateValueAt($i, $propertyPath, $value, $constraints
             ->willReturn($contextualValidator);
         $contextualValidator->expects($this->at(2 * $i + 1))
             ->method('validate')
-            ->with($value, $constraints, $group);
+            ->with($value, $constraints, $group)
+            ->willReturn($contextualValidator);
     }
 
     protected function assertNoViolation()