(Reuters) - European shares edged lower for the second straight session on Friday, as investors feared a new U.S. law backing protesters in Hong Kong would cloud the prospects of a preliminary Sino-U.S. trade deal.On Thursday, China warned of "firm counter measures" to the law supporting anti-government protesters in Hong Kong. The editor of China's state-backed Global Times tabloid said later in a tweet those could include barring drafters of the legislation from mainland China, Hong Kong and..