In ~BrowserToolbarGtk, remove notifications we added in the ctor....

chrome/browser/gtk/browser_toolbar_gtk.cc

Index: chrome/browser/gtk/browser_toolbar_gtk.cc
===================================================================
--- chrome/browser/gtk/browser_toolbar_gtk.cc	(revision 30237)
+++ chrome/browser/gtk/browser_toolbar_gtk.cc	(working copy)
@@ -93,6 +93,12 @@
 }
 
 BrowserToolbarGtk::~BrowserToolbarGtk() {
+  browser_->command_updater()->RemoveCommandObserver(IDC_BACK, this);
+  browser_->command_updater()->RemoveCommandObserver(IDC_FORWARD, this);
+  browser_->command_updater()->RemoveCommandObserver(IDC_RELOAD, this);
+  browser_->command_updater()->RemoveCommandObserver(IDC_HOME, this);
+  browser_->command_updater()->RemoveCommandObserver(IDC_BOOKMARK_PAGE, this);
+
   offscreen_entry_.Destroy();
 
   // When we created our MenuGtk objects, we pass them a pointer to our accel