Fixes uncaught exception in memory plugin on IE6/7

The memory plugin uses document.getElementsByTagName in order to count
the number of certain types of DOM elements. It uses (function).call() to
do this. In IE6/7 the getElementsByTagName is not a typical function and
does not have call(). This patch wraps the underlying function in an
anonymous function when call() is missing.
(cherry picked from commit 2eb2a6e02032623e9cce96feab30ac47e62b1ec6)

Signed-off-by: Philip Tellis <philip.tellis@gmail.com>