Move megamorphic cache table into the Dart heap.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 0c992e107299e90b5e28aabe6b28ebb5fd0192bd..379287a67b4f94a77a36c0263c45cb0529b70d12 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -1544,7 +1544,7 @@ void Isolate::Shutdown() {
 
     if (FLAG_trace_isolates) {
       heap()->PrintSizes();
-      megamorphic_cache_table()->PrintSizes();
+      MegamorphicCacheTable::PrintSizes(this);
       Symbols::DumpStats();
       OS::Print("[-] Stopping isolate:\n"
                 "\tisolate:    %s\n", name());
@@ -1623,9 +1623,6 @@ void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
   // Visit objects in the class table.
   class_table()->VisitObjectPointers(visitor);
 
-  // Visit objects in the megamorphic cache.
-  megamorphic_cache_table()->VisitObjectPointers(visitor);
-
   // Visit objects in per isolate stubs.
   StubCode::VisitObjectPointers(visitor);