Fix grammar and consistent use of URL / UI PART

un-postponing. I don't think this completely covers the UI text though? Let's see. I grepped for " an URL" (case insensitive) and also for " url" and " Url" and found UI text that should be fixed in:

(and yes, I know many of these are in tests, but they are still text that is displayed in the UI if you run the tests)

(and I'm not sure if config schema descriptions are considered UI text or not? I think they may be shown on config translate forms, but not sure)

modules/views_ui/src/Tests/DisplayTest.php:    $this->assertLink(t('Custom URL'), 0, 'The link option has custom url as summary.');
modules/search/src/Tests/SearchBlockTest.php:      'Submitted to correct url.'
modules/search/src/Tests/SearchBlockTest.php:      'Redirected to correct url.'
modules/system/src/Tests/File/UrlRewritingTest.php:    $this->assertEqual($GLOBALS['base_url'] . '/' . $filepath . '?foo=', $url, 'Correctly generated url. The query string is present.');
modules/system/src/Tests/File/UrlRewritingTest.php:    $this->assertEqual($GLOBALS['base_url'] . '/' . $filepath . '?foo=bar', $url, 'Correctly generated url. The query string is present.');
modules/system/src/Tests/File/UrlRewritingTest.php:    $this->assertEqual($GLOBALS['base_url'] . '/' . $filepath . '#v1.2', $url, 'Correctly generated url. The fragment is present.');
modules/system/src/Tests/File/UrlRewritingTest.php:    $this->assertEqual($GLOBALS['base_url'] . '/' . $filepath . '?foo=bar#v1.2', $url, 'Correctly generated url. The query string amd fragment is present.');
modules/system/src/Tests/Form/ConfirmFormTest.php:    $message = ($message ? $message : SafeMarkup::format('Cancel link with url %url found.', ['%url' => $url->toString()]));
modules/system/src/Tests/Form/RedirectTest.php:    $this->assertUrl($expected, [], 'Redirected to correct url/query.');
modules/system/src/Tests/Form/RedirectTest.php:    $this->assertUrl($expected, [], 'Redirected to correct url/query.');
modules/path/src/Plugin/migrate/source/UrlAliasBase.php:      'language' => $this->t('The language code of the url alias.'),
modules/path/src/Plugin/migrate/destination/UrlAlias.php:      'alias' => 'The url alias.',
modules/path/src/Plugin/migrate/destination/UrlAlias.php:      'langcode' => 'The language code for the url.',
modules/menu_ui/src/Tests/MenuTest.php:    $this->assertLinkByHref('admin/structure/menu/manage/' . $menu_name . '/add', 0, "The add menu link button url is correct");
modules/aggregator/src/Tests/AddFeedTest.php:    $this->assertUrl(\Drupal::url('aggregator.feed_add', [], 'absolute' => TRUE]), [], 'Directed to correct url.');
modules/aggregator/aggregator.module:        'description' => t('An icon that links to the feed url'),
modules/views/src/Tests/Plugin/StyleOpmlTest.php:    $this->assertEqual($outline[0]['url'], $feed->getUrl(), 'The correct url attribute is used for link OPML.');
modules/views/src/Plugin/views/argument/StringArgument.php:      '#description' => $this->t('When printing url paths, how to transform the case of the filter value. Do not use this unless with Postgres as it uses case sensitive comparisons.'),
modules/views/src/Plugin/views/field/FieldPluginBase.php:        '#description' => $this->t('When printing url paths, how to transform the case of the filter value.'),
modules/views/src/Plugin/views/display/DisplayPluginBase.php:        'desc' => $this->t('Specify which display or custom url this display will link to.'),
modules/views/src/Plugin/views/display/DisplayPluginBase.php:          '#description' => $this->t("This will add a more link to the bottom of this view, which will link to the page view. If you have more than one page view, the link will point to the display specified in 'Link display' section under pager. You can over
ride the url at the link display setting."),
modules/views/src/Plugin/views/row/OpmlFields.php:      '#description' => $this->t('The field that is going to be used as the OPML url attribute for each row.'),
modules/link/config/schema/link.schema.yml:          label: 'Is this Url absolute'
modules/link/config/schema/link.schema.yml:          label: 'If the Url should use a secure protocol'

Working on it

@jhodgdon according to your comment have the changes.
Url -> URL
url -> URL

Thanks! This patch looks perfect to me. All of the capitalization changes are correct as far as I can tell, and in addition, you've covered all of the spots I listed in #3. Great job!

Committed/pushed to 8.1.x, thanks!