Mark 'front()' and 'back()' as noexcept for array/deque/string/string_view. These are just rebranded 'operator[]', and should be noexcept like it is.

llvm-svn: 356435
diff --git a/libcxx/test/std/strings/string.view/string.view.access/front.pass.cpp b/libcxx/test/std/strings/string.view/string.view.access/front.pass.cpp
index 554ed1b..eb71389 100644
--- a/libcxx/test/std/strings/string.view/string.view.access/front.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.access/front.pass.cpp
@@ -18,7 +18,10 @@
 
 template <typename CharT>
 bool test ( const CharT *s, size_t len ) {
-    std::basic_string_view<CharT> sv ( s, len );
+    typedef std::basic_string_view<CharT> SV;
+    SV sv ( s, len );
+    ASSERT_SAME_TYPE(decltype(sv.front()), typename SV::const_reference);
+    LIBCPP_ASSERT_NOEXCEPT(   sv.front());
     assert ( sv.length() == len );
     assert ( sv.front() == s[0] );
     return &sv.front() == s;