Correctly handle problematic nested escapes in URL paths.
Specifically, if unescaping in the input leads to the output URL
containing a new escaped sequence, e.g. converting the input "%%30%30" to "%00", escape the leading '%' as "%25" to ensure the output sequence is not treated as a new valid escape sequence.
This ensures that canonicalizing the same URL a second time won't make changes
to it, which is important for avoiding crashes and other bugs in a variety of
places in both debug and release builds.
BUG=533361
TEST=Visit http://andrisatteka.blogspot.com/2015/09/a-simple-string-to-crash-google-chrome.html , hover the link there, Chrome should not crash.
Review URL: https://codereview.chromium.org/1358433004
Cr-Commit-Position: refs/heads/master@{#350086}
2 files changed
