fixed linter error - 'missing use strict'
fixed linter error - 'missing use strict'

josh-bernstein/cesium,progsung/cesium,jasonbeverage/cesium,YonatanKra/cesium,CesiumGS/cesium,CesiumGS/cesium,CesiumGS/cesium,progsung/cesium,likangning93/cesium,YonatanKra/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,jasonbeverage/cesium,YonatanKra/cesium,likangning93/cesium,likangning93/cesium,YonatanKra/cesium,likangning93/cesium,josh-bernstein/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium