Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

chrome/renderer/safe_browsing/phishing_classifier_delegate.cc

 // Copyright (c) 2011 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 "chrome/renderer/safe_browsing/phishing_classifier_delegate.h"
 
 #include <memory>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 271 matching lines @@
 
   DVLOG(2) << "Starting classification for " << last_finished_load_url_;
   last_url_sent_to_classifier_ = last_finished_load_url_;
   is_classifying_ = true;
   classifier_->BeginClassification(
       &classifier_page_text_,
       base::Bind(&PhishingClassifierDelegate::ClassificationDone,
                  base::Unretained(this)));
 }
 
+void PhishingClassifierDelegate::OnDestruct() {
+  delete this;
+}
+
 }  // namespace safe_browsing