Don't double apply an xobject's matrix and bbox.

When an xobject is a group we were double applying the matrix and
bounding box.

This improves mozilla#6961 quite a bit, but it still is missing the indention
in the ruler.

src/core/evaluator.js

@@ -527,7 +527,10 @@ class PartialEvaluator {
       operatorList.addOp(OPS.beginGroup, [groupOptions]);
     }
 
-    operatorList.addOp(OPS.paintFormXObjectBegin, [matrix, bbox]);
+    // If it's a group, beginGroup will handle setting the matrix and bbox,
+    // otherwise paintFormXObjectBegin will apply it.
+    const args = group ? [null, null] : [matrix, bbox];
+    operatorList.addOp(OPS.paintFormXObjectBegin, args);
 
     return this.getOperatorList({
       stream: xobj,