[clang-format] Fix regression merging comments across newlines.

Summary:
This fixes a regression that causes example:
```
enum A {
  a, // line a

  // line b
  b
};
```
to be formatted as follows:
```
enum A {
  a, // line a
     // line b
  b
};
```

Reviewers: djasper, klimek

Reviewed By: klimek

Subscribers: cfe-commits, sammccall, djasper, klimek

Differential Revision: https://reviews.llvm.org/D29322

llvm-svn: 293624

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index c10a13f39e0..a96d4d9be3e 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2124,7 +2124,12 @@ void UnwrappedLineParser::flushComments(bool NewlineBeforeNext) {
        I != E; ++I) {
     // Line comments that belong to the same line comment section are put on the
     // same line since later we might want to reflow content between them.
-    // See BreakableToken.
+    // Additional fine-grained breaking of line comment sections is controlled
+    // by the class BreakableLineCommentSection in case it is desirable to keep
+    // several line comment sections in the same unwrapped line.
+    //
+    // FIXME: Consider putting separate line comment sections as children to the
+    // unwrapped line instead.
     if (isOnNewLine(**I) && JustComments && !continuesLineComment(**I, *Line))
       addUnwrappedLine();
     pushToken(*I);