[crankshaft] Remove the useless HCallStub instruction.

src/crankshaft/x87/lithium-codegen-x87.cc

Index: src/crankshaft/x87/lithium-codegen-x87.cc
diff --git a/src/crankshaft/x87/lithium-codegen-x87.cc b/src/crankshaft/x87/lithium-codegen-x87.cc
index d358d6a03e3ee82063ae8d6358e55dffc47db275..78f0daf785e5c2366488df081950efc5f4789abe 100644
--- a/src/crankshaft/x87/lithium-codegen-x87.cc
+++ b/src/crankshaft/x87/lithium-codegen-x87.cc
@@ -1277,26 +1277,6 @@ void LCodeGen::DoParameter(LParameter* instr) {
 }
 
 
-void LCodeGen::DoCallStub(LCallStub* instr) {
-  DCHECK(ToRegister(instr->context()).is(esi));
-  DCHECK(ToRegister(instr->result()).is(eax));
-  switch (instr->hydrogen()->major_key()) {
-    case CodeStub::RegExpExec: {
-      RegExpExecStub stub(isolate());
-      CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
-    case CodeStub::SubString: {
-      SubStringStub stub(isolate());
-      CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-      break;
-    }
-    default:
-      UNREACHABLE();
-  }
-}
-
-
 void LCodeGen::DoUnknownOSRValue(LUnknownOSRValue* instr) {
   GenerateOsrPrologue();
 }