Use Browser::ShowSyncSetup from NTP sign in link
Use Browser::ShowSyncSetup from NTP sign in link

Clicking on the NTP sign in link now calls Browser::ShowSyncSetup(). This has two benefits:
  - consolidates the show the sync promo code
  - fix a bug where if the promo was already visible in a 2nd tab then the current NTP page would become blank

BUG=100484
TEST=


Review URL: http://codereview.chromium.org/9592042

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@125339 0039d316-1c4b-4281-b951-d872f2087c98

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