message: Run GradientTape test with both graph and eager execution.
  Test was introduced in
  This is a follow up change to tweak the test to a style that works for both
  graph and eager.
diff: @@ -1123,9 +1123,8 @@ class BackpropTest(test.TestCase):
  with self.cached_session() as sess:
  self.assertEqual((8.0, 12.0), sess.run((b, db_da), feed_dict={a: 2.0}))
  - def testCustomGradientTapeGraph(self):
  - with ops.Graph().as_default(), self.cached_session():
  -
  + @test_util.run_in_graph_and_eager_modes
  + def testCustomGradientInEagerAndGraph(self):
  @custom_gradient.custom_gradient
  def f(x):
  y = x * x
  @@ -1139,8 +1138,7 @@ class BackpropTest(test.TestCase):
  c = constant_op.constant(1.0)
  t.watch(c)
  g = f(c)
  - self.assertAllEqual(t.gradient(g, c).eval(), 4.0)
  -
  + self.assertAllEqual(self.evaluate(t.gradient(g, c)), 4.0)
  if __name__ == '__main__':
  test.main()
  