remove most uses of Isolate::Current in arch specific files

src/ia32/assembler-ia32-inl.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 311 matching lines @@
 }
 
 
 Immediate::Immediate(Label* internal_offset) {
   x_ = reinterpret_cast<int32_t>(internal_offset);
   rmode_ = RelocInfo::INTERNAL_REFERENCE;
 }
 
 
 Immediate::Immediate(Handle<Object> handle) {
-#ifdef DEBUG
-  Isolate* isolate = Isolate::Current();
-#endif
   AllowDeferredHandleDereference using_raw_address;
   // Verify all Objects referred by code are NOT in new space.
   Object* obj = *handle;
-  ASSERT(!isolate->heap()->InNewSpace(obj));
   if (obj->IsHeapObject()) {
+    ASSERT(!HeapObject::cast(obj)->GetHeap()->InNewSpace(obj));
     x_ = reinterpret_cast<intptr_t>(handle.location());
     rmode_ = RelocInfo::EMBEDDED_OBJECT;
   } else {
     // no relocation needed
     x_ =  reinterpret_cast<intptr_t>(obj);
     rmode_ = RelocInfo::NONE32;
   }
 }
 
 
@@ skipping 169 matching lines @@
 
 Operand::Operand(int32_t disp, RelocInfo::Mode rmode) {
   // [disp/r]
   set_modrm(0, ebp);
   set_dispr(disp, rmode);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_INL_H_