By Miyoung Kim SEOUL (Reuters) – As the smartphone action shifts to the mass market, leaders Samsung Electronics Co Ltd and Apple Inc are under pressure to make their high-end phones more affordable to revive sales. Samsung, which said on Tuesday it would likely post a second straight quarterly profit decline, has knocked around a tenth off the price of its Galaxy S5 in South Korea, in the first such move for a marquee smartphone launch – the S5 rolls out globally on Friday. The mass market – where a smartphone can be had for as little as $25 – is the new mobile device battleground, as high-end growth eases off with sales slowing in mature markets. Japan, for example, may see smartphone shipments shrink this year, according to researcher IDC.