Fix build broken at 8388037a5c58
Fix build broken at 8388037a5c58

Missing explicit include of <vector>

TBR=dsinclair@chromium.org

Review URL: https://codereview.chromium.org/1783433004 .

DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium,DrAlexx/pdfium