Adds support for running unittests using XCTest on iOS.

base/test/test_suite.cc

Index: base/test/test_suite.cc
diff --git a/base/test/test_suite.cc b/base/test/test_suite.cc
index 512bde5810a349dc6cc2f8a3a39db86d8d28daf7..f9bf38ea2d67ee19333dda0fdd6f11039c9fa439 100644
--- a/base/test/test_suite.cc
+++ b/base/test/test_suite.cc
@@ -238,7 +238,13 @@ int TestSuite::Run() {
   // Check to see if we are being run as a client process.
   if (!client_func.empty())
     return multi_process_function_list::InvokeChildProcessTest(client_func);
+
 #if defined(OS_IOS)
+  if (IsRunningWithXCTest()) {
+    // XCTest will drive the tests if running in XCTest mode on iOS.  There is
+    // no need to run the tests here or to tear down the test suite.
+    return 0;
+  }
   test_listener_ios::RegisterTestEndListener();
 #endif