Get rid of the HInstanceSize 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 7001c18f34ed129a6a5dc0d96b6b42c472071a0e..e9c533dcab878a18ef0445a1a4f79ebad9e5edaa 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1074,12 +1074,6 @@ LInstruction* LChunkBuilder::DoInstanceOfKnownGlobal(
 }
 
 
-LInstruction* LChunkBuilder::DoInstanceSize(HInstanceSize* instr) {
-  LOperand* object = UseRegisterAtStart(instr->object());
-  return DefineAsRegister(new(zone()) LInstanceSize(object));
-}
-
-
 LInstruction* LChunkBuilder::DoWrapReceiver(HWrapReceiver* instr) {
   LOperand* receiver = UseRegister(instr->receiver());
   LOperand* function = UseRegisterAtStart(instr->function());