[webcrypto] Implement encrypt() and importKey() for AES-CBC using NSS.

BUG=245025
R=bryaneyler@google.com, rsleevi@chromium.org

Review URL: https://codereview.chromium.org/23441078

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225689 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225689
Memory FYI cleanup: suppress some reports, remove an obsolete suppression
TBR=eugenis
NOTRY=true
BUG=268924,299647,107699

Review URL: https://codereview.chromium.org/25017002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225690 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225690