Added a comment and another test for the UT_ForIndentation option

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191530 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/WhitespaceManager.cpp b/lib/Format/WhitespaceManager.cpp
index 802145e..16d80ea 100644
--- a/lib/Format/WhitespaceManager.cpp
+++ b/lib/Format/WhitespaceManager.cpp
@@ -290,6 +290,8 @@
   case FormatStyle::UT_ForIndentation:
     if (WhitespaceStartColumn == 0) {
       unsigned Indentation = IndentLevel * Style.IndentWidth;
+      // This happens, e.g. when a line in a block comment is indented less than
+      // the first one.
       if (Indentation > Spaces)
         Indentation = Spaces;
       unsigned Tabs = Indentation / Style.TabWidth;