[Isolates] Avoid dereferencing Isolate::Current() to check oddball identities...

src/string-stream.cc

Index: src/string-stream.cc
===================================================================
--- src/string-stream.cc	(revision 5190)
+++ src/string-stream.cc	(working copy)
@@ -377,9 +377,10 @@
 
 
 void StringStream::PrintFixedArray(FixedArray* array, unsigned int limit) {
+  Heap* heap = HEAP;
   for (unsigned int i = 0; i < 10 && i < limit; i++) {
     Object* element = array->get(i);
-    if (element != HEAP->the_hole_value()) {
+    if (element != heap->the_hole_value()) {
       for (int len = 1; len < 18; len++)
         Put(' ');
       Add("%d: %o\n", i, array->get(i));
@@ -532,10 +533,11 @@
 void StringStream::PrintPrototype(JSFunction* fun, Object* receiver) {
   Object* name = fun->shared()->name();
   bool print_name = false;
-  for (Object* p = receiver; p != HEAP->null_value(); p = p->GetPrototype()) {
+  Heap* heap = HEAP;
+  for (Object* p = receiver; p != heap->null_value(); p = p->GetPrototype()) {
     if (p->IsJSObject()) {
       Object* key = JSObject::cast(p)->SlowReverseLookup(fun);
-      if (key != HEAP->undefined_value()) {
+      if (key != heap->undefined_value()) {
         if (!name->IsString() ||
             !key->IsString() ||
             !String::cast(name)->Equals(String::cast(key))) {