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

chrome/browser/ui/webui/options/clear_browser_data_handler.cc

Index: chrome/browser/ui/webui/options/clear_browser_data_handler.cc
===================================================================
--- chrome/browser/ui/webui/options/clear_browser_data_handler.cc	(revision 84869)
+++ chrome/browser/ui/webui/options/clear_browser_data_handler.cc	(working copy)
@@ -21,9 +21,8 @@
 }
 
 ClearBrowserDataHandler::~ClearBrowserDataHandler() {
-  if (remover_) {
+  if (remover_)
     remover_->RemoveObserver(this);
-  }
 }
 
 void ClearBrowserDataHandler::Initialize() {
@@ -125,6 +124,11 @@
   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),