Fix segmentation fault encountered on some systems during
TestSurfacePlot.

Fix "invalid read" errors within vtkChartXYZ (reported by valgrind)

Fix "variable shadowing" warning within RecalculateBounds()

Make it so we recalculate which points are clipped when we zoom
in or out using the mouse wheel.

Change-Id: Iaa3246bfec900e33e02122a5f1045e0ba7de8942