reverted:
--- b/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
+++ /dev/null
@@ -1,131 +0,0 @@
-<?php
-
-namespace Drupal\file\Plugin\Field\FieldType;
-
-use Drupal\Component\Utility\Bytes;
-use Drupal\Core\Form\FormStateInterface;
-use Drupal\Core\StringTranslation\TranslatableMarkup;
-
-/**
- * Provides helper methods for max file size value validation.
- */
-class FileItemMaxFileSizeValidator {
-
-  /**
-   * Holds a string representing a byte size to be validated.
-   *
-   * @var string
-   *   A string size expressed as a number of bytes with optional SI
-   *   or IEC binary unit prefix (e.g. 2, 3K, 5MB, 10G, 6GiB, 8 bytes, 9mbytes).
-   */
-  private static $size;
-
-  /**
-   * Form API callback.
-   *
-   * Ensures that a size has been entered and that it can be parsed by
-   * \Drupal\Component\Utility\Bytes::toInt().
-   *
-   * This function is assigned as an #element_validate callback in
-   * fieldSettingsForm().
-   * @param array $element
-   *   A field element array.
-   * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current state of the form.
-   */
-  public static function validateMaxFilesize(array $element, FormStateInterface $form_state) {
-
-    // Spaces are irrelevant to us. Bytes::toInt will process with or without
-    // them. Make our lives easier by just doing away with them.
-    self::$size = self::stripSpacesFromString($element['#value']);
-
-    // Having removed whitespace, if our string is now empty then the user
-    // either entered nothing or a string of whitespace. Accept both cases as
-    // valid.
-    if (empty(self::$size)) {
-      return;
-    }
-
-    // Theoretically self::stringIsValidByteString() should perform strict
-    // enough validation. Passing the string to Bytes::toInt() for added
-    // precaution.
-    if (self::sizeIsValidByteString() || !self::toIntCanParseString()) {
-      $translatable_markup = new TranslatableMarkup('The "@name" option must contain a valid value. You may either leave the text field empty or enter a string like "512" (bytes), "80 KB" (kilobytes) or "50 MB" (megabytes).', ['@name' => $element['#title']]);
-      $form_state->setError($element, $translatable_markup);
-    }
-  }
-
-  /**
-   * Validate the given string looks like a byte size string.
-   *
-   * @return bool
-   */
-  private static function sizeIsValidByteString() {
-    return (
-      self::sizeIsNotAlphaNumeric() ||
-      self::sizeNotStartWithNumber() ||
-      self::sizeHasNumbersFollowingAlphaChar()
-    );
-  }
-
-  /**
-   * Strips spaces from a string of text.
-   *
-   * @param string $string
-   *   A string representing a size (5mb, 500GB etc)
-   *
-   * @return string
-   *   Returns the inputted string with spaces removed.
-   */
-  private static function stripSpacesFromString($string) {
-    return trim(preg_replace('/\s+/', '', $string));
-  }
-
-  /**
-   * Determines that a string does not start with a number.
-   *
-   * @return bool
-   *   TRUE if the string does not start with a numeric char, FALSE otherwise.
-   */
-  private static function sizeNotStartWithNumber() {
-    return !preg_match('/^\d/', self::$size);
-  }
-
-  /**
-   * Determines if a string has numberic chars following after alpha chars.
-   *
-   * @return bool
-   *   TRUE if the string has numeric values following after alpha chars.
-   */
-  private static function sizeHasNumbersFollowingAlphaChar() {
-    return (bool) preg_match('/[a-zA-Z]+(\d+)/', self::$size);
-  }
-
-  /**
-   * Determines if a string contains non alphanumeric characters.
-   *
-   * @return bool
-   *   Returns TRUE if non alphanumeric characters are found.
-   */
-  private static function sizeIsNotAlphaNumeric() {
-    return (bool) !preg_match('/^[a-zA-Z0-9]+$/', self::$size);
-  }
-
-  /**
-   * Determines if Bytes:toInt() is able to parse the given string.
-   *
-   * @return bool
-   *   TRUE if string can be parsed by Bytes::toInt(), FALSE otherwise.
-   */
-  private static function toIntCanParseString() {
-    $valid = TRUE;
-    try {
-      Bytes::toInt(self::$size);
-    }
-    catch (\Exception $e) {
-      $valid = FALSE;
-    }
-    return $valid;
-  }
-
-}
reverted:
--- b/core/modules/file/tests/src/Unit/FileItemFieldSettingsFormTest.php
+++ /dev/null
@@ -1,92 +0,0 @@
-<?php
-
-namespace Drupal\Tests\file\Unit;
-
-use Drupal\Core\Form\FormState;
-use Drupal\Core\StringTranslation\TranslatableMarkup;
-use Drupal\file\Plugin\Field\FieldType\FileItemMaxFileSizeValidator;
-use Drupal\Tests\UnitTestCase;
-use Prophecy\Argument;
-
-/**
- * Tests FileItem's settings form's validation.
- *
- * @group file
- */
-class FileItemFieldSettingsFormTest extends UnitTestCase {
-
-  /**
-   * Tests that a sane Max file size is entered.
-   *
-   * @dataProvider maxFileSizeInputsProvider
-   */
-  public function testValidateMaxfilesize($input, $should_error) {
-
-    $element = [
-      '#title' => 'Maximum upload size',
-      '#value' => $input,
-    ];
-
-    $form_state = $this->prophesize(FormState::class);
-    if ($should_error) {
-      $form_state->setError($element, Argument::type(TranslatableMarkup::class))
-        ->shouldBeCalled();
-    }
-    else {
-      $form_state->setError($element, Argument::type(TranslatableMarkup::class))
-        ->shouldNotBeCalled();
-    }
-    FileItemMaxFileSizeValidator::validateMaxFilesize($element, $form_state->reveal());
-
-  }
-
-  /**
-   * Data provider for testValidateMaxfilesize().
-   *
-   * @return array[]
-   *   Array of inputs and error expectations.
-   */
-  public function maxFileSizeInputsProvider() {
-    return [
-      ['0 bytes', FALSE],
-      ['123456.03 ', TRUE],
-      ['   ', FALSE],
-      ['', FALSE],
-      ['0 K', FALSE],
-      ['100bytes', FALSE],
-      ['10000', FALSE],
-      ['100bytes', FALSE],
-      ['100 bytes', FALSE],
-      ['999989 bytes', FALSE],
-      ['999989bytes', FALSE],
-      ['2', FALSE],
-      ['3K', FALSE],
-      ['5MB', FALSE],
-      ['10G', FALSE],
-      ['6GiB', FALSE],
-      ['8bytes', FALSE],
-      ['9mbytes', FALSE],
-      // Should we allow these spaces?
-      ['1 0 0 0 0 m b y tes', FALSE],
-      ['nonumbers', TRUE],
-      ['bread', TRUE],
-      ['bananas', TRUE],
-      ['1234b1', TRUE],
-      ['543xd1', TRUE],
-      ['-1', TRUE],
-      ['-975', TRUE],
-      [' word ', TRUE],
-      [' word', TRUE],
-      ['word ', TRUE],
-      [' words with spaces ', TRUE],
-      ['words with spaces ', TRUE],
-      [' words with spaces', TRUE],
-      [' 123456 ', FALSE],
-      [' 123456.03 ', TRUE],
-      ['123456.03 ', TRUE],
-      [' 123456.03', TRUE],
-      [' some words & stuff', TRUE],
-    ];
-  }
-
-}
only in patch2:
unchanged:
--- a/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
+++ b/core/modules/file/src/Plugin/Field/FieldType/FileItemMaxFileSizeValidator.php
@@ -37,7 +37,7 @@ public static function validateMaxFilesize(array $element, FormStateInterface $f
 
     // Spaces are irrelevant to us. Bytes::toInt will process with or without
     // them. Make our lives easier by just doing away with them.
-    self::$size = self::stripSpacesFromString($element['#value']);
+    self::$size = self::stripWhitespaceFromString($element['#value']);
 
     // Having removed whitespace, if our string is now empty then the user
     // either entered nothing or a string of whitespace. Accept both cases as
@@ -77,7 +77,7 @@ private static function sizeIsValidByteString() {
    * @return string
    *   Returns the inputted string with spaces removed.
    */
-  private static function stripSpacesFromString($string) {
+  private static function stripWhitespaceFromString($string) {
     return trim(preg_replace('/\s+/', '', $string));
   }