Allow a profile without extension service to show notification.  ChromeOS needs to be able to show notification before a user logged in (such as battery, update notification).  Currently, all attempt to show notification results in crash because BalloonHost assume all profile has  extension service, which is not the case for login profile that ChromeOS uses.
Allow a profile without extension service to show notification.
 ChromeOS needs to be able to show notification before a user logged in (such as battery, update notification).
 Currently, all attempt to show notification results in crash because BalloonHost assume all profile has
 extension service, which is not the case for login profile that ChromeOS uses.

 John, I didn't ifdef'ed because BalloonHost is not assuming extension_function_dispacher is allways present.
 Please let me now if I should limit this change to OS_CHROMEOS.

BUG=http://crosbug.com/3491
TEST=none

Review URL: http://codereview.chromium.org/2221003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@48403 0039d316-1c4b-4281-b951-d872f2087c98

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