Improves EXPECT_DEATH_IF_SUPPORTED to allow streaming of messages and enforcing the validity of arguments (by Vlad Losev); adds samples for the event listener API (by Vlad Losev); simplifies the tests using EXPECT_DEATH_IF_SUPPORTED (by Zhanyong Wan).

test/gtest_unittest.cc

@@ -6345,16 +6345,14 @@ TEST(EventListenerTest, SuppressEventForwarding) {
   EXPECT_EQ(0, on_start_counter);
 }
 
-#if GTEST_HAS_DEATH_TEST
 // Tests that events generated by Google Test are not forwarded in
 // death test subprocesses.
 TEST(EventListenerDeathTest, EventsNotForwardedInDeathTestSubprecesses) {
-  EXPECT_DEATH({  // NOLINT
+  EXPECT_DEATH_IF_SUPPORTED({
       GTEST_CHECK_(EventListenersAccessor::EventForwardingEnabled(
           *GetUnitTestImpl()->listeners())) << "expected failure";},
       "expected failure");
 }
-#endif  // GTEST_HAS_DEATH_TEST
 
 // Tests that a listener installed via SetDefaultResultPrinter() starts
 // receiving events and is returned via default_result_printer() and that