The iPhone saw its share of the worldwide smartphone market shrink in the fourth quarter of 2009, according to a new report. Citing data from ABI Research, the Wall Street Journal reports that the iPhone’s share of worldwide smartphone sales dipped from 18.1% in the third quarter to 16.6% in the fourth quarter, despite the fact that iPhone sales increased 18% to 8.7 million units during the same time period. According to the report, the overall…