Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

components/printing/renderer/print_web_view_helper.cc

 // Copyright (c) 2012 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 "components/printing/renderer/print_web_view_helper.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <string>
 #include <utility>
@@ skipping 924 matching lines @@
 #endif  // defined(ENABLE_PRINT_PREVIEW)
     IPC_MESSAGE_HANDLER(PrintMsg_SetScriptedPrintingBlocked,
                         SetScriptedPrintBlocked)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
   --ipc_nesting_level_;
   return handled;
 }
 
+void PrintWebViewHelper::OnDestruct() {
+  delete this;
+}
+
 bool PrintWebViewHelper::GetPrintFrame(blink::WebLocalFrame** frame) {
   DCHECK(frame);
   blink::WebView* webView = render_view()->GetWebView();
   DCHECK(webView);
   if (!webView)
     return false;
 
   // If the user has selected text in the currently focused frame we print
   // only that frame (this makes print selection work for multiple frames).
   blink::WebLocalFrame* focusedFrame =
@@ skipping 1290 matching lines @@
       blink::WebConsoleMessage::LevelWarning, message));
   return false;
 }
 
 void PrintWebViewHelper::ScriptingThrottler::Reset() {
   // Reset counter on successful print.
   count_ = 0;
 }
 
 }  // namespace printing