Remove the allow-displaying-mixed-content setting from Blink.

components/test_runner/test_preferences.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_TEST_RUNNER_TEST_PREFERENCES_H_
 #define COMPONENTS_TEST_RUNNER_TEST_PREFERENCES_H_
 
 #include "components/test_runner/test_runner_export.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/platform/WebURL.h"
 #include "third_party/WebKit/public/web/WebSettings.h"
 
 namespace blink {
 class WebView;
 }
 
 namespace test_runner {
 
 struct TEST_RUNNER_EXPORT TestPreferences {
     int default_font_size;
     int minimum_font_size;
     bool xss_auditor_enabled;
-    bool allow_display_of_insecure_content;
     bool allow_file_access_from_file_urls;
     bool allow_running_of_insecure_content;
     blink::WebString default_text_encoding_name;
     bool experimental_webgl_enabled;
     bool experimental_css_grid_layout_enabled;
     bool java_script_can_access_clipboard;
     bool java_script_can_open_windows_automatically;
     bool supports_multiple_windows;
     bool java_script_enabled;
     bool loads_images_automatically;
@@ skipping 11 matching lines @@
     bool strict_powerful_feature_restrictions;
     bool spatial_navigation_enabled;
 
     TestPreferences();
     void Reset();
 };
 
 }
 
 #endif  // COMPONENTS_TEST_RUNNER_TEST_PREFERENCES_H_