chromium: multiple issues

• CVE-2015-6788 (arbitrary code execution)

A type confusion vulnerability has been discovered in the handling of
extensions that could possibly lead to arbitrary code execution.

• CVE-2015-6789 (arbitrary code execution)

A use-after free vulnerability has been discovered in Blink that could
possibly lead to arbitrary code execution.

• CVE-2015-6790 (insufficient escaping)

An escaping issue has been discovered in saved pages that has
unspecified impact.

• CVE-2015-6791 (multiple issues)

Various unspecified vulnerabilities have been discovered from internal
audits, fuzzing and other initiatives.