Fix renderer crashes when frame gets detached while injectng user scripts.

components/autofill/content/renderer/page_click_tracker.cc

 // Copyright 2013 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/autofill/content/renderer/page_click_tracker.h"
 
 #include "components/autofill/content/renderer/form_autofill_util.h"
 #include "components/autofill/content/renderer/page_click_listener.h"
 #include "content/public/renderer/render_view.h"
 #include "third_party/WebKit/public/platform/WebString.h"
@@ skipping 73 matching lines @@
   const WebInputElement input_element =
       GetTextWebInputElement(last_node_clicked_);
   if (input_element.isNull())
     return;
 
   bool is_focused = (last_node_clicked_ == render_view()->GetFocusedNode());
   listener_->InputElementClicked(input_element, was_focused_, is_focused);
 }
 
 void PageClickTracker::DidFinishDocumentLoad(blink::WebFrame* frame) {
+  if (frame->document().isNull())
+    return;
   tracked_frames_.push_back(frame);
   frame->document().addEventListener("mousedown", this, false);
 }
 
 void PageClickTracker::FrameDetached(blink::WebFrame* frame) {
   std::vector<blink::WebFrame*>::iterator iter =
       std::find(tracked_frames_.begin(), tracked_frames_.end(), frame);
   if (iter == tracked_frames_.end()) {
     // Some frames might never load contents so we may not have a listener on
     // them.  Calling removeEventListener() on them would trigger an assert, so
@@ skipping 33 matching lines @@
   was_focused_ = (node.document().focusedNode() == last_node_clicked_);
 }
 
 void PageClickTracker::HandleTextFieldMaybeLosingFocus(
     const WebNode& newly_clicked_node) {
   if (DidSelectedTextFieldLoseFocus(newly_clicked_node))
     listener_->InputElementLostFocus();
 }
 
 }  // namespace autofill