Move megamorphic cache table into the Dart heap.

runtime/vm/flow_graph_compiler_arm64.cc

Index: runtime/vm/flow_graph_compiler_arm64.cc
diff --git a/runtime/vm/flow_graph_compiler_arm64.cc b/runtime/vm/flow_graph_compiler_arm64.cc
index 11bc02db2c00b7852e92c3db03510eaae692fb51..f7ce841bb8f3ea3b09cd7eafafe65a3c6400379a 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -1257,13 +1257,12 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
     intptr_t deopt_id,
     intptr_t token_pos,
     LocationSummary* locs) {
-  MegamorphicCacheTable* table = Isolate::Current()->megamorphic_cache_table();
   const String& name = String::Handle(zone(), ic_data.target_name());
   const Array& arguments_descriptor =
       Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
   ASSERT(!arguments_descriptor.IsNull() && (arguments_descriptor.Length() > 0));
-  const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(
-      zone(), table->Lookup(name, arguments_descriptor));
+  const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
+      MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
   const Register receiverR = R0;
   const Register cacheR = R1;
   const Register targetR = R1;