Move test into test/std subdirectory.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@224658 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/time/time.duration/time.duration.arithmetic/op_+=.pass.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <chrono>
+
+// duration
+
+// duration& operator+=(const duration& d);
+
+#include <chrono>
+#include <cassert>
+
+int main()
+{
+    std::chrono::seconds s(3);
+    s += std::chrono::seconds(2);
+    assert(s.count() == 5);
+    s += std::chrono::minutes(2);
+    assert(s.count() == 125);
+}