[Isolates] Add heap pointer to all maps and use map->heap() more.

src/heap-profiler.cc

Index: src/heap-profiler.cc
diff --git a/src/heap-profiler.cc b/src/heap-profiler.cc
index d2d9ad9d0e658f9b19747410858edd452ce511fd..7fbeee0ab459955f4fe50b75915e20e5fa976128 100644
--- a/src/heap-profiler.cc
+++ b/src/heap-profiler.cc
@@ -412,9 +412,7 @@ HeapSnapshot* HeapProfiler::FindSnapshot(unsigned uid) {
 
 
 void HeapProfiler::ObjectMoveEvent(Address from, Address to) {
-  HeapProfiler* profiler = Isolate::Current()->heap_profiler();
-  ASSERT(profiler != NULL);
-  profiler->snapshots_->ObjectMoveEvent(from, to);
+  snapshots_->ObjectMoveEvent(from, to);
 }