[Isolates] Replace ISOLATE_FROM_HEAP with Heap::isolate()

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 2df89c3d1cb1320eac434ae7279bb730713d3d98..c6fed5803cf6fa90a58f0d258aae220c5dcdc265 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1035,12 +1035,6 @@ class Isolate {
 };
 
 
-#define ISOLATE_FROM_HEAP(heap_pointer) ((Isolate*)(  \
-  (uint8_t*)(heap_pointer) -                          \
-  (size_t)((Isolate*)sizeof(Isolate))->heap() +       \
-  sizeof(Isolate)))
-
-
 // If the GCC version is 4.1.x or 4.2.x an additional field is added to the
 // class as a work around for a bug in the generated code found with these
 // versions of GCC. See V8 issue 122 for details.