Add a genuine unary minus instruction to Crankshaft....

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 6698)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1253,6 +1253,12 @@
 }
 
 
+LInstruction* LChunkBuilder::DoNeg(HNeg* instr) {
+  Abort("Unimplemented: %s", "DoNeg");
+  return NULL;
+}
+
+
 LInstruction* LChunkBuilder::DoBitOr(HBitOr* instr) {
   return DoBit(Token::BIT_OR, instr);
 }