Pass the node to the onRender callback in TeX
Pass the node to the onRender callback in TeX

Summary:
We need to pass the node for the TeX component when the onRender
callback fires so that the perseus callback can take that node
and measure it so that it can be scaled to fit.

Test Plan: see test plan from https://phabricator.khanacademy.org/D27575

Reviewers: david, charlie

Reviewed By: charlie

Differential Revision: https://phabricator.khanacademy.org/D27573

Khan/react-components,Khan/react-components,Khan/react-components