clang-format: Improve clang-format's detection about comment binding.

Before, existing code in the form of:

  int a; // this is a.
  // This is
  // b.
  int b;

Got turned into:

  int a; // this is a.
         // This is
  // b.
  int b;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194294 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Format/FormatTest.cpp b/unittests/Format/FormatTest.cpp
index 794fb1a..e37f0cd 100644
--- a/unittests/Format/FormatTest.cpp
+++ b/unittests/Format/FormatTest.cpp
@@ -787,6 +787,26 @@
                    "// first\n"
                    " // at start\n"
                    "otherLine();   // comment"));
+  verifyFormat("f(); // comment\n"
+               "// first\n"
+               "// at start\n"
+               "otherLine();");
+  EXPECT_EQ("f(); // comment\n"
+            "// first\n"
+            "// at start\n"
+            "otherLine();",
+            format("f();   // comment\n"
+                   "// first\n"
+                   " // at start\n"
+                   "otherLine();"));
+  EXPECT_EQ("f(); // comment\n"
+            "     // first\n"
+            "// at start\n"
+            "otherLine();",
+            format("f();   // comment\n"
+                   " // first\n"
+                   "// at start\n"
+                   "otherLine();"));
 }
 
 TEST_F(FormatTest, CanFormatCommentsLocally) {