PlzNavigate: Move navigation-level mixed content checks to the browser.

content/shell/browser/shell.h

Index: content/shell/browser/shell.h
diff --git a/content/shell/browser/shell.h b/content/shell/browser/shell.h
index 545af236cba83da6714edc080e8126e19680fdb9..27cfd9b90b850fd702210ef4f416e1d94d8149f0 100644
--- a/content/shell/browser/shell.h
+++ b/content/shell/browser/shell.h
@@ -167,6 +167,10 @@ class Shell : public WebContentsDelegate,
       WebContents* source,
       const WebContentsUnresponsiveState& unresponsive_state) override;
   void ActivateContents(WebContents* contents) override;
+  bool ShouldAllowRunningInsecureContent(content::WebContents* web_contents,
+                                         bool allowed_per_prefs,
+                                         const url::Origin& origin,
+                                         const GURL& resource_url) override;
 
   static gfx::Size GetShellDefaultSize();