feat(testability): Expose function frameworkStabilizers

Closes #5485

modules/playground/e2e_test/async/async_spec.ts

@@ -58,5 +58,35 @@ describe('async', () => {
     expect(timeout.$('.val').getText()).toEqual('10');
   });
 
+  it('should wait via frameworkStabilizer', () => {
+    var whenAllStable = function() {
+      return browser.executeAsyncScript('window.frameworkStabilizers[0](arguments[0]);');
+    };
+
+    // This disables protractor's wait mechanism
+    browser.ignoreSynchronization = true;
+
+    var timeout = $('#multiDelayedIncrements');
+
+    // At this point, the async action is still pending, so the count should
+    // still be 0.
+    expect(timeout.$('.val').getText()).toEqual('0');
+
+    timeout.$('.action').click();
+
+    whenAllStable().then((didWork) => {
+      // whenAllStable should only be called when all the async actions
+      // finished, so the count should be 10 at this point.
+      expect(timeout.$('.val').getText()).toEqual('10');
+      expect(didWork).toBeTruthy();  // Work was done.
+    });
+
+    whenAllStable().then((didWork) => {
+      // whenAllStable should be called immediately since nothing is pending.
+      expect(didWork).toBeFalsy();  // No work was done.
+      browser.ignoreSynchronization = false;
+    });
+  });
+
   afterEach(verifyNoBrowserErrors);
 });