SAN FRANCISCO — Amazon.com Inc's revenue grew more than expected for the first quarter, largely offset by a sharp increase in spending on technology, content and new warehouses as the e-commerce company branches into new businesses.Amazon's international unit, which accounts for 40 percent of sales, continued to be a drag as sales growth slowed to 18 percent during the quarter. Global unit sales, a closely watched measure of how many items Amazon has sold, also decelerated, rising only 23 percent.The company is investing heavily in new markets abroad, particularly China, where it faces tough competition with Chinese e-commerce company Alibaba.This week alone, Amazon unveiled two initiatives to stem defections, including a deal to stream older shows from HBO, the premium cable channel owned by Time Warner Inc.