extensions: darken some disabled text for better contrast.

This is the Accessibility Developer Tools suggested color
for a 4.5 contrast ratio (minimum for AA rating[1] /
audit to stop barking).

R=kalman@chromium.org
BUG=439227

[1] http://www.w3.org/WAI/WCAG2AA-Conformance

Review URL: https://codereview.chromium.org/893603006

Cr-Commit-Position: refs/heads/master@{#314022}

chrome/browser/resources/extensions/extensions.css

@@ -236,7 +236,7 @@ html[dir='rtl'] .extension-list-item {
 .location-text,
 .blacklist-text,
 .enable-checkbox input:disabled + .enable-checkbox-text {
-  color: rgb(151, 156, 160);
+  color: rgb(115, 119, 122);
 }
 
 .enable-controls {

chrome/browser/ui/webui/extensions/extension_settings_browsertest.js

@@ -30,18 +30,6 @@ ExtensionSettingsWebUITest.prototype = {
   /** @override */
   accessibilityIssuesAreErrors: true,
 
-  /** @override */
-  setUp: function() {
-    // TODO(aboxhall): remove these when crbug.com/267035 is closed.
-    this.accessibilityAuditConfig.ignoreSelectors(
-      'lowContrastElements',
-      '.enable-checkbox input:disabled + .enable-checkbox-text > *');
-    this.accessibilityAuditConfig.ignoreSelectors(
-      'lowContrastElements', '.extension-description > *');
-    this.accessibilityAuditConfig.ignoreSelectors(
-      'lowContrastElements', '.location-text');
-  },
-
   /**
    * A URL to load before starting each test.
    * @type {string}