Montgomery County officials agreed to rethink parts of their massive White Flint redevelopment plan after widespread opposition broke out to measures that critics said would have crippled the area with traffic. Dozens of neighborhood activists, retail and development representatives, and self-styled “smart growth” proponents crammed themselves into the Montgomery County Council chambers Monday afternoon after flooding the economic development committee’s e-mail and voicemail message boxes with angry denunciations of a plan to widen Rockville Pike and to replace the median on Montrose Road with reversible lanes. Their message got through: Members of the economic development committee, led by Marc Elrich, D-at large, agreed to shelve the road proposals. Montgomery officials are weighing a plan that would convert the area around the White Flint Metro station from an area of strip malls and car dealerships to a dense, skyscraper-dominated urban center.