Add a null check for the target node in page_click_tracker.

chrome/renderer/page_click_tracker.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 "chrome/renderer/page_click_tracker.h"
 
 #include "chrome/common/render_messages.h"
 #include "chrome/renderer/autofill/form_autofill_util.h"
 #include "chrome/renderer/page_click_listener.h"
 #include "content/public/renderer/render_view.h"
@@ skipping 114 matching lines @@
 
   const WebDOMMouseEvent mouse_event = event.toConst<WebDOMMouseEvent>();
   DCHECK(mouse_event.buttonDown());
   if (mouse_event.button() != 0)
     return;  // We are only interested in left clicks.
 
   // Remember which node has focus before the click is processed.
   // We'll get a notification once the mouse event has been processed
   // (DidHandleMouseEvent), we'll notify the listener at that point.
   WebNode node = mouse_event.target();
+  if (node.isNull())
+    // Node may be null if the target was an SVG instance element from a <use>
+    // tree and the tree has been rebuilt due to an earlier event.
+    return;
 
   HandleTextFieldMaybeLosingFocus(node);
 
   // We are only interested in text field clicks.
   if (GetTextWebInputElement(node).isNull())
     return;
 
   last_node_clicked_ = node;
   was_focused_ = (node.document().focusedNode() == last_node_clicked_);
 }
 
 void PageClickTracker::HandleTextFieldMaybeLosingFocus(
     const WebNode& newly_clicked_node) {
   if (!DidSelectedTextFieldLoseFocus(newly_clicked_node))
     return;
 
   ObserverListBase<PageClickListener>::Iterator it(listeners_);
   PageClickListener* listener;
   while ((listener = it.GetNext()) != NULL) {
     if (listener->InputElementLostFocus())
       break;
   }
 }