clang-format: Properly align ObjC string literals.

Before:
  NSString s = @"a"
               "b"
               "c";
  NSString s = @"a"
               @"b"
                @"c";

After:
  NSString s = @"a"
                "b"
                "c";
  NSString s = @"a"
               @"b"
               @"c";

This fixes llvm.org/PR23536.

llvm-svn: 237538
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index f3a875b..f7510c8 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -4768,7 +4768,11 @@
   verifyFormat("f(@\"a\"\n"
                "  @\"b\");");
   verifyFormat("NSString s = @\"a\"\n"
-               "             @\"b\";");
+               "             @\"b\"\n"
+               "             @\"c\";");
+  verifyFormat("NSString s = @\"a\"\n"
+               "              \"b\"\n"
+               "              \"c\";");
 }
 
 TEST_F(FormatTest, AlwaysBreakAfterDefinitionReturnType) {