add updateSize() API method to Popup

[euzuro]

Instead of hiding the auto-sizing code in the setContentHTML() function, let's bring it out into it's own, updateSize() api function so that others can use it.

[euzuro]

all tests pass in ff2, ie7.

There are no specific tests for this change, but there is the acceptance test in /examples/popupMatrix.html, and I can verify that all is good there.

please review.

[euzuro]

(In [7886]) Bubble out the code that handles the re-sizing of the popup into an APIMethod: updateSize(). Other change is that now instead of using the 'contentHTML' string property to autosize, we will now use the actual contentDiv's 'innerHTML' property. This is possible because in the setContentHTML() function, we switch around the order and set the conentDiv.innerHTML *before* calling updateSize(). Seemingly minor, this change actually does wonders towards distancing us from the horrendous idea that the 'contentHTML' property was in the first place. Now, if users go in and fudge with the contentDiv DOMElement directly, they can still benefit from the auto-sizing. In fact, 'contentHTML' can be totally ignored altogether. joy. All tests pass, including an eyeballing of the acceptance test examples/popupMatrix.html in ff2 and ie7. Mil gracias to cr5 for the speedy review (Closes #1708)