Exclude filler maps from object properties in heap snapshot.

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index f722795f4857d73e75616f02d4929abf4b8e3e03..bf149a64dd9dbdc6f3e35706949084285e167802 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -2490,7 +2490,10 @@ bool V8HeapExplorer::IsEssentialObject(Object* object) {
       && object != heap_->raw_unchecked_empty_descriptor_array()
       && object != heap_->raw_unchecked_fixed_array_map()
       && object != heap_->raw_unchecked_global_property_cell_map()
-      && object != heap_->raw_unchecked_shared_function_info_map();
+      && object != heap_->raw_unchecked_shared_function_info_map()
+      && object != heap_->raw_unchecked_free_space_map()
+      && object != heap_->raw_unchecked_one_pointer_filler_map()
+      && object != heap_->raw_unchecked_two_pointer_filler_map();
 }