[clang-format] Move OriginalPrefix from base to subclass.

Summary:
OriginalPrefix is only needed for line comment sections. Moved from the base class to the child class.
No functional changes.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D29716

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@294457 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Format/BreakableToken.h

@@ -282,10 +282,6 @@ protected:
   // line.
   bool FirstInLine;
 
-  // In case of line comments, holds the original prefix, including trailing
-  // whitespace.
-  SmallVector<StringRef, 16> OriginalPrefix;
-
   // The prefix to use in front a line that has been reflown up.
   // For example, when reflowing the second line after the first here:
   // // comment 1
@@ -394,6 +390,14 @@ private:
   unsigned getContentStartColumn(unsigned LineIndex,
                                  unsigned TailOffset) const override;
 
+  // OriginalPrefix[i] contains the original prefix of line i, including
+  // trailing whitespace before the start of the content. The indentation
+  // preceding the prefix is not included.
+  // For example, if the line is:
+  // // content
+  // then the original prefix is "// ".
+  SmallVector<StringRef, 16> OriginalPrefix;
+
   // Prefix[i] contains the intended leading "//" with trailing spaces to
   // account for the indentation of content within the comment at line i after
   // formatting. It can be different than the original prefix when the original