bug 832837 - move insecure form submission warning from nsSecureBrowserUIImpl to the HTML form implementation r=mrbkap r=phlsa

As a result, we can remove nsSecurityWarningDialogs completely, which this patch also does.

dom/html/HTMLFormElement.h

@@ -495,6 +495,16 @@ protected:
   nsresult NotifySubmitObservers(nsIURI* aActionURL, bool* aCancelSubmit,
                                  bool aEarlyNotify);
 
+  /**
+   * If this form submission is secure -> insecure, ask the user if they want
+   * to continue.
+   *
+   * @param aActionURL the URL being submitted to
+   * @param aCancelSubmit out param: will be true if the user wants to cancel
+   */
+  nsresult DoSecureToInsecureSubmitCheck(nsIURI* aActionURL,
+                                         bool* aCancelSubmit);
+
   /**
    * Find form controls in this form with the correct value in the name
    * attribute.