Adds some debugging code in hopes of identifying a crasher.

chrome/browser/ui/views/tabs/default_tab_drag_controller.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/browser/ui/views/tabs/default_tab_drag_controller.h"
 
 #include <math.h>
 #include <set>
 
 #include "base/callback.h"
 #include "base/i18n/rtl.h"
 #include "chrome/browser/extensions/extension_function_dispatcher.h"
 #include "chrome/browser/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/app_modal_dialogs/message_box_handler.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/tabs/base_tab.h"
 #include "chrome/browser/ui/views/tabs/base_tab_strip.h"
 #include "chrome/browser/ui/views/tabs/browser_tab_strip_controller.h"
 #include "chrome/browser/ui/views/tabs/dragged_tab_view.h"
 #include "chrome/browser/ui/views/tabs/native_view_photobooth.h"
 #include "chrome/browser/ui/views/tabs/tab.h"
 #include "chrome/browser/ui/views/tabs/tab_strip.h"
 #include "content/browser/tab_contents/tab_contents.h"
 #include "content/browser/user_metrics.h"
 #include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "grit/theme_resources.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/animation/animation.h"
 #include "ui/base/animation/animation_delegate.h"
 #include "ui/base/animation/slide_animation.h"
 #include "ui/base/events.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/canvas_skia.h"
@@ skipping 316 matching lines @@
 
   // Listen for Esc key presses.
   MessageLoopForUI::current()->AddObserver(this);
 
   if (source_tab->width() > 0) {
     offset_to_width_ratio_ = static_cast<float>(source_tab_offset_) /
         static_cast<float>(source_tab->width());
   }
   InitWindowCreatePoint();
   initial_selection_model_.Copy(initial_selection_model);
+
+  registrar_.Add(
+      this,
+      content::NOTIFICATION_TAB_CONTENTS_DELEGATE_DESTROYED,
+      content::NotificationService::AllSources());
 }
 
 void DefaultTabDragController::InitTabDragData(BaseTab* tab,
                                                TabDragData* drag_data) {
   drag_data->source_model_index =
       source_tabstrip_->GetModelIndexOfBaseTab(tab);
   drag_data->contents = GetModel(source_tabstrip_)->GetTabContentsAt(
       drag_data->source_model_index);
   drag_data->pinned = source_tabstrip_->IsTabPinned(tab);
   registrar_.Add(
@@ skipping 91 matching lines @@
   return GetJavaScriptDialogCreatorInstance();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // DefaultTabDragController, content::NotificationObserver implementation:
 
 void DefaultTabDragController::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
+  if (type == content::NOTIFICATION_TAB_CONTENTS_DELEGATE_DESTROYED) {
+    TabContentsDelegate* delegate =
+        content::Source<TabContentsDelegate>(source).ptr();
+    for (size_t i = 0; i < drag_data_.size(); ++i)
+      CHECK_NE(delegate, drag_data_[i].original_delegate);
+    return;
+  }
   DCHECK_EQ(type, content::NOTIFICATION_TAB_CONTENTS_DESTROYED);
   TabContents* destroyed_contents = content::Source<TabContents>(source).ptr();
   for (size_t i = 0; i < drag_data_.size(); ++i) {
     if (drag_data_[i].contents->tab_contents() == destroyed_contents) {
       // One of the tabs we're dragging has been destroyed. Cancel the drag.
       if (destroyed_contents->delegate() == this)
         destroyed_contents->set_delegate(NULL);
       drag_data_[i].contents = NULL;
       drag_data_[i].original_delegate = NULL;
       EndDragImpl(TAB_DESTROYED);
@@ skipping 926 matching lines @@
   controller->Init(source_tabstrip, source_tab, tabs, mouse_offset,
                    source_tab_offset, initial_selection_model);
   return controller;
 }
 
 // static
 bool TabDragController::IsAttachedTo(BaseTabStrip* tab_strip) {
   return instance_ && instance_->active()&&
       instance_->attached_tabstrip() == tab_strip;
 }