Add safe part of previous (reverted) commit, necessary to update to LLVM API change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82540 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/StmtProfile.cpp

@@ -237,7 +237,7 @@ void StmtProfiler::VisitImaginaryLiteral(ImaginaryLiteral *S) {
 
 void StmtProfiler::VisitStringLiteral(StringLiteral *S) {
   VisitExpr(S);
-  ID.AddString(S->getStrData(), S->getStrData() + S->getByteLength());
+  ID.AddString(S->getString());
   ID.AddBoolean(S->isWide());
 }