Chromium-browser-stable 51.0.2704.63 fixes security issues:
cross-origin bypass problems in extensions bindings (CVE-2016-1672 and CVE-2016-1676), blink (CVE-2016-1673 and CVE-2016-1675), and extensions (CVE-2016-1674)
heap use-after free bugs in V8 bindings (CVE-2016-1679), Skia (CVE-2016-1680), and Autofill (CVE-2016-1690)
heap buffer overflows in V8 (CVE-2016-1678), PDFium (CVE-2016-1681), media (CVE-2016-1689), and Skia (CVE-2016-1691)
out-of-bounds read errors in PDFium (CVE-2016-1685 and CVE-2016-1686) and V8 (CVE-2016-1688)
type confusion in V8 (CVE-2016-1677), a CSP bypass for ServiceWorker (CVE-2016-1682), an information leak in extensions (CVE-2016-1687), a limited cross-origin bypass in ServiceWorker (CVE-2016-1692), and HPKP pins removed on cache clearance (CVE-2016-1694)
various fixes from upstream's internal audits, fuzzing, and other initiatives (CVE-2016-1695)