Remove unnecessary AST node for ++ and -- operations.

src/prettyprinter.cc

Index: src/prettyprinter.cc
===================================================================
--- src/prettyprinter.cc	(revision 7507)
+++ src/prettyprinter.cc	(working copy)
@@ -376,11 +376,6 @@
 }
 
 
-void PrettyPrinter::VisitIncrementOperation(IncrementOperation* node) {
-  UNREACHABLE();
-}
-
-
 void PrettyPrinter::VisitCountOperation(CountOperation* node) {
   Print("(");
   if (node->is_prefix()) Print("%s", Token::String(node->op()));
@@ -1056,11 +1051,6 @@
 }
 
 
-void AstPrinter::VisitIncrementOperation(IncrementOperation* node) {
-  UNREACHABLE();
-}
-
-
 void AstPrinter::VisitCountOperation(CountOperation* node) {
   EmbeddedVector<char, 128> buf;
   if (node->type()->IsKnown()) {
@@ -1461,11 +1451,6 @@
 }
 
 
-void JsonAstBuilder::VisitIncrementOperation(IncrementOperation* expr) {
-  UNREACHABLE();
-}
-
-
 void JsonAstBuilder::VisitCountOperation(CountOperation* expr) {
   TagScope tag(this, "CountOperation");
   {