dom-ui settings: Stop observing an existing BrowserDataRemover before creating a new one.

chrome/browser/ui/webui/options/clear_browser_data_handler.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/webui/options/clear_browser_data_handler.h"
 
 #include "base/basictypes.h"
 #include "base/string16.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "content/common/notification_details.h"
 #include "grit/chromium_strings.h"
 #include "grit/generated_resources.h"
 #include "grit/locale_settings.h"
 #include "ui/base/l10n/l10n_util.h"
 
 ClearBrowserDataHandler::ClearBrowserDataHandler() : remover_(NULL) {
 }
 
 ClearBrowserDataHandler::~ClearBrowserDataHandler() {
-  if (remover_) {
+  if (remover_)
     remover_->RemoveObserver(this);
-  }
 }
 
 void ClearBrowserDataHandler::Initialize() {
   clear_plugin_lso_data_enabled_.Init(prefs::kClearPluginLSODataEnabled,
                                       g_browser_process->local_state(),
                                       NULL);
 }
 
 void ClearBrowserDataHandler::GetLocalizedValues(
     DictionaryValue* localized_strings) {
@@ skipping 81 matching lines @@
     remove_mask |= BrowsingDataRemover::REMOVE_PASSWORDS;
   if (prefs->GetBoolean(prefs::kDeleteFormData))
     remove_mask |= BrowsingDataRemover::REMOVE_FORM_DATA;
 
   int period_selected = prefs->GetInteger(prefs::kDeleteTimePeriod);
 
   FundamentalValue state(true);
   web_ui_->CallJavascriptFunction("ClearBrowserDataOverlay.setClearingState",
                                   state);
 
+  // If we are still observing a previous data remover, we need to stop
+  // observing.
+  if (remover_)
+    remover_->RemoveObserver(this);
+
   // BrowsingDataRemover deletes itself when done.
   remover_ = new BrowsingDataRemover(profile,
       static_cast<BrowsingDataRemover::TimePeriod>(period_selected),
       base::Time());
   remover_->AddObserver(this);
   remover_->Remove(remove_mask);
 }
 
 void ClearBrowserDataHandler::OnBrowsingDataRemoverDone() {
   // No need to remove ourselves as an observer as BrowsingDataRemover deletes
   // itself after we return.
   remover_ = NULL;
   DCHECK(web_ui_);
   web_ui_->CallJavascriptFunction("ClearBrowserDataOverlay.doneClearing");
 }