Escapes backslash, colon, comma, equals and semicolon in IAccessible2 string attributes.

This is a requirement of the IAccessible2 object attributes specification and is affecting NVDA.
BUG=540974
R=aboxhall@chromium.org, dmazzoni@chromium.org, dtseng@chromium.org

Review URL: https://codereview.chromium.org/1397183002

Cr-Commit-Position: refs/heads/master@{#353671}
3 files changed