Disentangle assembler from isolate.

src/x87/macro-assembler-x87.cc

Index: src/x87/macro-assembler-x87.cc
diff --git a/src/x87/macro-assembler-x87.cc b/src/x87/macro-assembler-x87.cc
index 37ca3856efc54a25b3e587fd0e9b95960a560a1c..badfa42eecf5413cda4a5c45a4af8c3a654c5366 100644
--- a/src/x87/macro-assembler-x87.cc
+++ b/src/x87/macro-assembler-x87.cc
@@ -19,14 +19,15 @@ namespace internal {
 // -------------------------------------------------------------------------
 // MacroAssembler implementation.
 
-MacroAssembler::MacroAssembler(Isolate* arg_isolate, void* buffer, int size,
+MacroAssembler::MacroAssembler(Isolate* isolate, void* buffer, int size,
                                CodeObjectRequired create_code_object)
     : Assembler(arg_isolate, buffer, size),
       generating_stub_(false),
-      has_frame_(false) {
+      has_frame_(false),
+      isolate_(isolate) {
   if (create_code_object == CodeObjectRequired::kYes) {
     code_object_ =
-        Handle<Object>::New(isolate()->heap()->undefined_value(), isolate());
+        Handle<Object>::New(isolate_->heap()->undefined_value(), isolate_);
   }
 }