clang-format: Don't generate unnecessary replacements for \r\n line endings.

Patch by Mathieu Champlon. Thank you.

llvm-svn: 239900
diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index e3e162d..e364986 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -345,7 +345,7 @@
   // Calculate the start of the non-whitespace text in the current line.
   size_t StartOfLine = Lines[LineIndex].find_first_not_of(Blanks);
   if (StartOfLine == StringRef::npos)
-    StartOfLine = Lines[LineIndex].size();
+    StartOfLine = Lines[LineIndex].rtrim("\r\n").size();
 
   StringRef Whitespace = Lines[LineIndex].substr(0, StartOfLine);
   // Adjust Lines to only contain relevant text.