Reapply "Move megamorphic cache table into the Dart heap."

runtime/vm/snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
@@ skipping 642 matching lines @@
 
   // The version string matches. Read the rest of the snapshot.
 
   // TODO(asiva): Add a check here to ensure we have the right heap
   // size for the full snapshot being read.
   {
     NoSafepointScope no_safepoint;
     HeapLocker hl(isolate, old_space());
 
     // Read in all the objects stored in the object store.
-    intptr_t num_flds = (object_store->to() - object_store->from());
+    RawObject** toobj = snapshot_code() ? object_store->to()
+                                        : object_store->to_snapshot();
+    intptr_t num_flds = (toobj - object_store->from());
     for (intptr_t i = 0; i <= num_flds; i++) {
       *(object_store->from() + i) = ReadObjectImpl(kAsInlinedObject);
     }
     for (intptr_t i = 0; i < backward_references_->length(); i++) {
       if (!(*backward_references_)[i].is_deserialized()) {
         ReadObjectImpl(kAsInlinedObject);
         (*backward_references_)[i].set_state(kIsDeserialized);
       }
     }
 
@@ skipping 1313 matching lines @@
     writer.ReserveHeader();
 
     // Write out the version string.
     writer.WriteVersion();
 
     // Write out the full snapshot.
 
     // Write out all the objects in the object store of the isolate which
     // is the root set for all dart allocated objects at this point.
     SnapshotWriterVisitor visitor(&writer, false);
-    object_store->VisitObjectPointers(&visitor);
+    visitor.VisitPointers(object_store->from(),
+                          snapshot_code_ ? object_store->to()
+                                         : object_store->to_snapshot());
 
     // Write out all forwarded objects.
     writer.WriteForwardedObjects();
 
     writer.FillHeader(writer.kind());
     writer.UnmarkAll();
 
     isolate_snapshot_size_ = writer.BytesWritten();
   } else {
     writer.ThrowException(writer.exception_type(), writer.exception_msg());
@@ skipping 776 matching lines @@
     NoSafepointScope no_safepoint;
     WriteObject(obj.raw());
     UnmarkAll();
   } else {
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart