Security update for Chromium (important)

This update to Chromium 55.0.2883.75 fixes the following vulnerabilities:

• CVE-2016-9651: Private property access in V8
• CVE-2016-5208: Universal XSS in Blink
• CVE-2016-5207: Universal XSS in Blink
• CVE-2016-5206: Same-origin bypass in PDFium
• CVE-2016-5205: Universal XSS in Blink
• CVE-2016-5204: Universal XSS in Blink
• CVE-2016-5209: Out of bounds write in Blink
• CVE-2016-5203: Use after free in PDFium
• CVE-2016-5210: Out of bounds write in PDFium
• CVE-2016-5212: Local file disclosure in DevTools
• CVE-2016-5211: Use after free in PDFium
• CVE-2016-5213: Use after free in V8
• CVE-2016-5214: File download protection bypass
• CVE-2016-5216: Use after free in PDFium
• CVE-2016-5215: Use after free in Webaudio
• CVE-2016-5217: Use of unvalidated data in PDFium
• CVE-2016-5218: Address spoofing in Omnibox
• CVE-2016-5219: Use after free in V8
• CVE-2016-5221: Integer overflow in ANGLE
• CVE-2016-5220: Local file access in PDFium
• CVE-2016-5222: Address spoofing in Omnibox
• CVE-2016-9650: CSP Referrer disclosure
• CVE-2016-5223: Integer overflow in PDFium
• CVE-2016-5226: Limited XSS in Blink
• CVE-2016-5225: CSP bypass in Blink
• CVE-2016-5224: Same-origin bypass in SVG
• CVE-2016-9652: Various fixes from internal audits, fuzzing and other
  initiatives

The default bookmarks override was removed.

The following packaging changes are included:

• Switch to system libraries: harfbuzz, zlib, ffmpeg, where available.
• Chromium now requires harfbuzz >= 1.3.0