Adds NULL check in NotifySessionServiceOfRestoredTabs for SessionService. This comes from crash data. Only way I could see this happening is if between the time we request the data from the backend and the time we get it the service is destroyed.
Adds NULL check in NotifySessionServiceOfRestoredTabs for
SessionService. This comes from crash data. Only way I could see this
happening is if between the time we request the data from the backend
and the time we get it the service is destroyed.

BUG=95125
TEST=none
R=marja@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10265010

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@134708 0039d316-1c4b-4281-b951-d872f2087c98

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