Remove code to handle FlateStream differently now that we have a sane interface

pdf.js

@@ -2458,13 +2458,7 @@ var CanvasGraphics = (function() {
                     var tokens = [];
                     var token = "";
 
-                    var length = cmapObj.length;
+                    var cmap = cmapObj.getBytes(cmapObj.length);
-                    if (cmapObj instanceof FlateStream) {
-                      cmapObj.readBlock();
-                      length = cmapObj.bufferLength;
-                    }
-
-                    var cmap = cmapObj.getBytes(length);
                     for (var i =0; i < cmap.length; i++) {
                       var byte = cmap[i];
                       if (byte == 0x20 || byte == 0x0A || byte == 0x3C || byte == 0x3E) {