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

content/public/common/web_preferences.cc

 // 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.
 
 #include "content/public/common/web_preferences.h"
 
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "third_party/WebKit/public/web/WebSettings.h"
@@ skipping 97 matching lines @@
       mock_scrollbars_enabled(false),
       accelerated_2d_canvas_enabled(false),
       minimum_accelerated_2d_canvas_size(257 * 256),
       disable_2d_canvas_copy_on_write(false),
       antialiased_2d_canvas_disabled(false),
       antialiased_clips_2d_canvas_enabled(false),
       accelerated_2d_canvas_msaa_sample_count(0),
       accelerated_filters_enabled(false),
       deferred_filters_enabled(false),
       container_culling_enabled(false),
-      allow_displaying_insecure_content(true),
       allow_running_insecure_content(false),
       disable_reading_from_canvas(false),
       strict_mixed_content_checking(false),
       strict_powerful_feature_restrictions(false),
       allow_geolocation_on_insecure_origins(false),
       strictly_block_blockable_mixed_content(false),
       block_mixed_plugin_content(false),
       password_echo_enabled(false),
       should_print_backgrounds(false),
       should_clear_document_background(true),
@@ skipping 98 matching lines @@
   pictograph_font_family_map[kCommonScript] =
       base::ASCIIToUTF16("Times New Roman");
 }
 
 WebPreferences::WebPreferences(const WebPreferences& other) = default;
 
 WebPreferences::~WebPreferences() {
 }
 
 }  // namespace content