CodeStubs contain their corresponding Isolate* now. (part 2)

test/cctest/test-code-stubs-x64.cc

Index: test/cctest/test-code-stubs-x64.cc
diff --git a/test/cctest/test-code-stubs-x64.cc b/test/cctest/test-code-stubs-x64.cc
index a63209ffa3125b28e41f7199a40e7078ce36cbd8..3ffd292c5f03b8ddeb7280edc2a7baaea531ce69 100644
--- a/test/cctest/test-code-stubs-x64.cc
+++ b/test/cctest/test-code-stubs-x64.cc
@@ -55,7 +55,7 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
   int offset =
     source_reg.is(rsp) ? 0 : (HeapNumber::kValueOffset - kSmiTagSize);
   DoubleToIStub stub(isolate, source_reg, destination_reg, offset, true);
-  byte* start = stub.GetCode(isolate)->instruction_start();
+  byte* start = stub.GetCode()->instruction_start();
 
   __ pushq(rbx);
   __ pushq(rcx);