Move megamorphic cache table into the Dart heap.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 2d7fc3aa63deb3cdf847c961ad9e4da071ded232..53ee195ace543e7719175ff59986f0ef3c47c9fa 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -1012,7 +1012,7 @@ DEFINE_RUNTIME_ENTRY(MegamorphicCacheMissHandler, 3) {
   const Array& descriptor = Array::CheckedHandle(arguments.ArgAt(2));
   const String& name = String::Handle(ic_data.target_name());
   const MegamorphicCache& cache = MegamorphicCache::Handle(
-      isolate->megamorphic_cache_table()->Lookup(name, descriptor));
+      MegamorphicCacheTable::Lookup(isolate, name, descriptor));
   Class& cls = Class::Handle(receiver.clazz());
   ASSERT(!cls.IsNull());
   if (FLAG_trace_ic || FLAG_trace_ic_miss_in_optimized) {