Revert 254089 "Use the default dispatcher where possible for nes..."

This is still breaking interactive-ui-tests on the win-dbg buildbots.

> Use the default dispatcher where possible for nested message loops.
> 
> Notable changes:
>  * Add QuitNestedMessageLoop() to client::DispatcherClient, which can be used to
>    terminate a nested loop started by RunWithDispatcher().
>  * FirstRunDialog and SimpleMessageBoxViews are no longer
>    MessagePumpDispatchers. The default dispatcher is used instead, and
>    QuitNestedMessageLoop() is called to terminate the loop instead of returning
>    POST_DISPATCH_QUIT_LOOP from the Dispatch() override.
> 
> BUG=none
> R=sky@chromium.org
> 
> Previously committed in r253723, but reverted in r253744 because it broke
> interactive_ui_tests on win-dbg.
> 
> Review URL: https://codereview.chromium.org/182143002

TBR=sadrul@chromium.org

Review URL: https://codereview.chromium.org/183683006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254095 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254095