@Override
  public void setRadius(float radius) {
    Preconditions.checkState(radius >= 0);
    Arrays.fill(mCornerRadii, radius);
    mRadiiNonZero = (radius != 0);
    mIsPathDirty = true;
    invalidateSelf();
  }
Specify radius for the corners of the rectangle. If this is > 0, then the drawable is drawn in
a round-rectangle, rather than a rectangle.

@param radius the radius for the corners of the rectangle
drawee/src/main/java/com/facebook/drawee/drawable/RoundedDrawable.java