b/3331379 reduce ping-to-zoom jitter.

    private static float MINIMUM_SCALE_INCREMENT = 0.01f;

    /*

     *  The touch points could be changed even the fingers stop moving.

     *  We use the following to filter out the zooming jitters.

     */

    private static float MINIMUM_SCALE_WITHOUT_JITTER = 0.05f;

    /*

     * The following member variables are only to be used for animating zoom. If

     * mZoomScale is non-zero then we are in the middle of a zoom animation. The

                } else {

                    scale = Math.max(scale, mActualScale * 0.8f);

                }

                // if the scale change is too small, regard it as jitter and skip it.

                if (Math.abs(scale - mActualScale) < MINIMUM_SCALE_WITHOUT_JITTER) {

                    return false;

                }

                setZoomCenter(detector.getFocusX(), detector.getFocusY());

                setZoomScale(scale, false);

                mWebView.invalidate();