Revert of Use the default dispatcher where possible for nested message loops. (https://codereview.chromium.org/182143002/)

Reason for revert:
win debug interactive_ui_tests:

BookmarkBarViewTest12.CloseWithModalDialog (run #1):
[ RUN      ] BookmarkBarViewTest12.CloseWithModalDialog
[3940:2156:0226/224958:2493504:FATAL:desktop_dispatcher_client.cc(33)] Check failed: !quit_closure_.is_null(). 

Original issue's description:
> 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
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=253723

TBR=sky@chromium.org,sadrul@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Review URL: https://codereview.chromium.org/182753002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253744 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253744