Added Ping-From and Ping-To headers associated with <a ping>.

The spec for <a ping> adds two new HTTP headers that may be sent with
a ping request. See
http://html.spec.whatwg.org/multipage/semantics.html#hyperlink-auditing.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=78456250
1 file changed