Add asserts to guard against regressions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182916 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Format/BreakableToken.cpp b/lib/Format/BreakableToken.cpp
index 10ba1f3..01317db 100644
--- a/lib/Format/BreakableToken.cpp
+++ b/lib/Format/BreakableToken.cpp
@@ -316,6 +316,7 @@
   unsigned BreakOffsetInToken =
       Text.data() - Tok.TokenText.data() + Split.first;
   unsigned CharsToRemove = Split.second;
+  assert(IndentAtLineBreak >= Decoration.size());
   Whitespaces.breakToken(Tok, BreakOffsetInToken, CharsToRemove, "", Prefix,
                          InPPDirective, IndentAtLineBreak - Decoration.size());
 }
@@ -347,6 +348,7 @@
   unsigned WhitespaceOffsetInToken =
       Lines[LineIndex].data() - Tok.TokenText.data() -
       LeadingWhitespace[LineIndex];
+  assert(StartOfLineColumn[LineIndex] >= Prefix.size());
   Whitespaces.breakToken(
       Tok, WhitespaceOffsetInToken, LeadingWhitespace[LineIndex], "", Prefix,
       InPPDirective, StartOfLineColumn[LineIndex] - Prefix.size());