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

components/test_runner/mock_content_settings_client.cc

Index: components/test_runner/mock_content_settings_client.cc
diff --git a/components/test_runner/mock_content_settings_client.cc b/components/test_runner/mock_content_settings_client.cc
index 5d41dc8cc1e498d75b4310643317cf09e9a2a037..b1dd7be9105bd62d8b1cd6a4c2736a6abab8824f 100644
--- a/components/test_runner/mock_content_settings_client.cc
+++ b/components/test_runner/mock_content_settings_client.cc
@@ -54,12 +54,6 @@ bool MockContentSettingsClient::allowPlugins(bool enabled_per_settings) {
   return enabled_per_settings && flags_->plugins_allowed();
 }
 
-bool MockContentSettingsClient::allowDisplayingInsecureContent(
-    bool enabled_per_settings,
-    const blink::WebURL& url) {
-  return enabled_per_settings || flags_->displaying_insecure_content_allowed();
-}
-
 bool MockContentSettingsClient::allowRunningInsecureContent(
     bool enabled_per_settings,
     const blink::WebSecurityOrigin& context,