Always destroy CrxInstaller on the UI Thread

chrome/browser/extensions/crx_installer.h

Index: chrome/browser/extensions/crx_installer.h
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index 7be80a6ed98efd66d11a35d68b8f9e14241a60aa..43b54f2f40ba4ac34671287a99957ece66e951b9 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -370,9 +370,7 @@ class CrxInstaller
 
   // The client we will work with to do the installation. This can be NULL, in
   // which case the install is silent.
-  // NOTE: we may be deleted on the file thread. To ensure the UI is deleted on
-  // the main thread we don't use a scoped_ptr here.
-  ExtensionInstallPrompt* client_;
+  scoped_ptr<ExtensionInstallPrompt> client_;
 
   // The root of the unpacked extension directory. This is a subdirectory of
   // temp_dir_, so we don't have to delete it explicitly.