clang-format: Support aligning ObjC string literals.

Before:
  NSString s = @"aaaa"
      @"bbbb";

After:
  NSString s = @"aaaa"
               @"bbbb";

llvm-svn: 237000
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 9098d2b..91540d4 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -4715,11 +4715,16 @@
                "  \"jkl\");");
 
   verifyFormat("f(L\"a\"\n"
-               "  L\"b\")");
+               "  L\"b\");");
   verifyFormat("#define A(X)            \\\n"
                "  L\"aaaaa\" #X L\"bbbbbb\" \\\n"
                "  L\"ccccc\"",
                getLLVMStyleWithColumns(25));
+
+  verifyFormat("f(@\"a\"\n"
+               "  @\"b\");");
+  verifyFormat("NSString s = @\"a\"\n"
+               "             @\"b\";");
 }
 
 TEST_F(FormatTest, AlwaysBreakAfterDefinitionReturnType) {
@@ -4817,9 +4822,9 @@
 
   // Exempt ObjC strings for now.
   EXPECT_EQ("NSString *const kString = @\"aaaa\"\n"
-            "                           \"bbbb\";",
+            "                          @\"bbbb\";",
             format("NSString *const kString = @\"aaaa\"\n"
-                   "\"bbbb\";",
+                   "@\"bbbb\";",
                    Break));
 
   Break.ColumnLimit = 0;