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

chrome/renderer/content_settings_observer.h

Index: chrome/renderer/content_settings_observer.h
diff --git a/chrome/renderer/content_settings_observer.h b/chrome/renderer/content_settings_observer.h
index 4ff25cfc90f214a4db1a2371e464017262bb27b4..324c360d2ac8acb0f89876f87daa7ab296954ad4 100644
--- a/chrome/renderer/content_settings_observer.h
+++ b/chrome/renderer/content_settings_observer.h
@@ -78,12 +78,11 @@ class ContentSettingsObserver
   void didNotAllowPlugins() override;
   void didNotAllowScript() override;
   void didUseKeygen() override;
-  bool allowDisplayingInsecureContent(bool allowed_per_settings,
-                                      const blink::WebURL& url) override;
   bool allowRunningInsecureContent(bool allowed_per_settings,
                                    const blink::WebSecurityOrigin& context,
                                    const blink::WebURL& url) override;
   bool allowAutoplay(bool default_value) override;
+  void passiveInsecureContentFound(const blink::WebURL&) override;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ContentSettingsObserverTest, WhitelistedSchemes);
@@ -131,7 +130,6 @@ class ContentSettingsObserver
 #endif
 
   // Insecure content may be permitted for the duration of this render view.
-  bool allow_displaying_insecure_content_;
   bool allow_running_insecure_content_;
 
   // A pointer to content setting rules stored by the renderer. Normally, the