Function moveArrowTail

test/jasmine/tests/gl3d_plot_interact_test.js:1869–1881

(dx, dy, expectation)

        }

        function moveArrowTail(dx, dy, expectation) {
            var px = 243;
            var py = 150;

            return new Promise(function(resolve) {
                gd.once('plotly_relayout', function(eventData) {
                    expect(eventData).toEqual(expectation);
                    resolve();
                });

                drag({pos0: [px, py], dpos: [dx, dy], noCover: true});
            });
        }

        Plotly.newPlot(gd, [{
            type: 'scatter3d',