Canvas arcTo() implementation bug in Firefox 3.5

Code for the black line

  context.moveTo(30,130);
  context.arcTo(30,20,280,20,40);
  // t1=30/60 t2=70/20

According to the Canvas specification, the current implementation of arcTo(x1, y1, x2, y2, radius) in Firefox 3.5 is incorrect.

The specification states: "The method must connect the point (x0, y0) to the start tangent point by a straight line, adding the start tangent point to the subpath, and then must connect the start tangent point to the end tangent point by The Arc, adding the end tangent point to the subpath."

Given this text, the line should end at the end tangent point t2 and not reach further to x2/y2.