Try using saveAs instead of exportDocument; it'll respect the name of the file you give it. The options are yours to change:
var myfile = "C:\\temp\\Google Analytics.png";
SavePNG(saveFile)
function savePNG(saveFile)
{
// save out the image
var pngFile = new File(filepath);
pngSaveOptions = new PNGSaveOptions();
pngSaveOptions.embedColorProfile = true;
pngSaveOptions.formatOptions = FormatOptions.STANDARDBASELINE;
pngSaveOptions.matte = MatteType.NONE;
pngSaveOptions.quality = 1;
activeDocument.saveAs(pngFile, pngSaveOptions, false, Extension.LOWERCASE);
}