Under pressure from China, Hong Kong has been chipping away at the territory’s free speech, which is a key pillar of the city’s identity. WSJ visits the set of “Headliner,” a popular satirical news show to find out how a proposed national security law could change the global hub. Photo/Video: Clément Bürge/WSJ Beijing has begun quietly delivering a message to Washington: U.S. pressure over matters China considers off limits could jeopardize Chinese purchases of farm goods and other U.S. exports under the “Phase One” trade deal. Chinese leaders have accused Washington of meddling in areas such as Hong Kong, where China is imposing a sweeping national-security law, and Taiwan, which Beijing considers as part of China. On Thursday, the U.S. Senate passed by unanimous consent a bill that would put sanctions on Chinese officials, businesses…