URL shortner for dashboards (#4760)

* Added support for URLShortLinkButton to work for the dashboard case

* Fix lint errors and test

* Change references to 'slice' to 'chart'.

* Add unit tests to improve coverage

* Fixing lint errors

* Refactor to make URLShortLink more generic. Remove history modification code, redirect should be handling this.

* Remove history modification code, redirect should be handling this

* Generate a shorter link without the directory, and delegate default linked to the contents of window.location

* Fix lint errors

* Fix test_shortner test to check for new pattern

* Remove usage of addHistory to manipulate explore shortlink redirection

* Address build failure and using better practices for shortlink defaults

* Fixing alphabetical order

* More syntax mistakes

* Revert explore view history changes

* Fix use of component props, & rebase

superset/assets/spec/javascripts/components/URLShortLinkButton_spec.jsx

@@ -0,0 +1,23 @@
+import React from 'react';
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+import { shallow } from 'enzyme';
+
+import { OverlayTrigger } from 'react-bootstrap';
+import URLShortLinkButton from '../../../src/components/URLShortLinkButton';
+
+describe('URLShortLinkButton', () => {
+  const defaultProps = {
+    url: 'mockURL',
+    emailSubject: 'Mock Subject',
+    emailContent: 'mock content',
+  };
+
+  it('renders', () => {
+    expect(React.isValidElement(<URLShortLinkButton {...defaultProps} />)).to.equal(true);
+  });
+  it('renders OverlayTrigger', () => {
+    const wrapper = shallow(<URLShortLinkButton {...defaultProps} />);
+    expect(wrapper.find(OverlayTrigger)).have.length(1);
+  });
+});