message: [XLA] Revise the way to express a CPU specific test.
  Use #ifdef XLA_TEST_BACKEND_CPU to protect the test instead of disabling it for
  all the other backends except for the CPU backend.
diff: @@ -764,9 +764,10 @@ XLA_TEST_F(FusionTest, Clamp2D) {
  TestElementwise2D<float, 3>(HloOpcode::kClamp);
  }
  -// TODO(b/117156505): Remove this test when the bug is fixed.
  -XLA_TEST_F(FusionTest, DISABLED_ON_GPU(DISABLED_ON_INTERPRETER(
  - LayoutChangingElementWiseOp))) {
  +// TODO(b/117156505): Remove this test when the bug is fixed and the CPU backend
  +// should not generate layout changing elementwise operations.
  +#ifdef XLA_TEST_BACKEND_CPU
  +XLA_TEST_F(FusionTest, LayoutChangingElementWiseOp) {
  const string hlo_text = R"(
  HloModule Cluster
  @@ -795,6 +796,7 @@ ENTRY main {
  LiteralUtil::CreateR3<float>({{{0.}, {0.76159415595}}, {{0.}, {0.}}}),
  result));
  }
  +#endif
  class FusionClientLibraryTest : public ClientLibraryTestBase {};
  