Refactor to use the right Element class (#13287)

Refactor to use the right Element class (#13287)

Changed implementations and APIs to use the non-deprecated Element class
wherever possible without breaking backwards compatibility.
* Methods defined in interfaces have not been touched.
* Return types have only been changed methods that should have no
existing third party callers (i.e. private, internal or @since 7.2)
* For methods that third party code might have overridden, the method
has been deprecated in favor of a new method that just delegates to the
old method.
* For methods that can't reasonably be overridden by third party code
(i.e. private, final, static, internal or @since 7.2), the parameter
type has been changed without retaining the old method.

Change-Id: I7da943a77b8d0d0b9185d8c70f87d676a275d24b