Steps:
1. Go to http://dev.w3.org/csswg/css3-transforms/#matrix-decomposing
2. Look at the following check for a coordinate system flip:

Actual:
scale[0] *= -1

should be

scale[i] *= -1

// At this point, the matrix (in rows) is orthonormal.
// Check for a coordinate system flip.  If the determinant
// is -1, then negate the matrix and the scaling factors.
pdum3 = cross(row[1], row[2])
if (dot(row[0], pdum3) < 0)
    for (i = 0; i < 3; i++)
        scale[0] *= -1;
        row[i][0] *= -1
        row[i][1] *= -1
        row[i][2] *= -1


Expected:

// At this point, the matrix (in rows) is orthonormal.
// Check for a coordinate system flip.  If the determinant
// is -1, then negate the matrix and the scaling factors.
pdum3 = cross(row[1], row[2])
if (dot(row[0], pdum3) < 0)
    for (i = 0; i < 3; i++)
        scale[i] *= -1;
        row[i][0] *= -1
        row[i][1] *= -1
        row[i][2] *= -1