Encode form data using the KeyedEncoder
https://bugs.webkit.org/show_bug.cgi?id=124107

Reviewed by Sam Weinig.

Source/WebCore:

* platform/KeyedCoding.h:
(WebCore::KeyedEncoder::encodeEnum):
* platform/network/FormData.cpp:
(WebCore::encodeElement):
(WebCore::FormData::encode):
* platform/network/FormData.h:

Source/WebKit2:

* Shared/cf/KeyedEncoder.cpp:
(WebKit::KeyedEncoder::encodeBool):
(WebKit::KeyedEncoder::encodeDouble):
* Shared/cf/KeyedEncoder.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159004 268f45cc-cd09-0410-ab3c-d52691b4dbfc