Remove unused HIsNumberAndBranch instruction.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 3a7366e324699dfdfb8ae6b3f42760298b0984e0..fcf2862da41ba29aa5a0173942773125ae37d1f7 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1911,12 +1911,6 @@ LInstruction* LChunkBuilder::DoCheckSmi(HCheckSmi* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoIsNumberAndBranch(HIsNumberAndBranch* instr) {
-  return new(zone()) LIsNumberAndBranch(
-      UseRegisterOrConstantAtStart(instr->value()));
-}
-
-
 LInstruction* LChunkBuilder::DoCheckInstanceType(HCheckInstanceType* instr) {
   LOperand* value = UseRegisterAtStart(instr->value());
   LCheckInstanceType* result = new(zone()) LCheckInstanceType(value);