[serializer] make snapshot reproducible.

src/snapshot/startup-serializer.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/snapshot/startup-serializer.h"
 
 #include "src/objects-inl.h"
 #include "src/v8threads.h"
 
 namespace v8 {
@@ skipping 95 matching lines @@
   CHECK_EQ(0, isolate->eternal_handles()->NumberOfHandles());
   // We don't support serializing installed extensions.
   CHECK(!isolate->has_installed_extensions());
   // First visit immortal immovables to make sure they end up in the first page.
   serializing_immortal_immovables_roots_ = true;
   isolate->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG_ROOT_LIST);
   // Check that immortal immovable roots are allocated on the first page.
   CHECK(HasNotExceededFirstPageOfEachSpace());
   serializing_immortal_immovables_roots_ = false;
   // Visit the rest of the strong roots.
+  // Clear the stack limits to make the snapshot reproducible.
+  // Reset it again afterwards.
+  isolate->heap()->ClearStackLimits();
   isolate->heap()->IterateSmiRoots(this);
+  isolate->heap()->SetStackLimits();
+
   isolate->heap()->IterateStrongRoots(this,
                                       VISIT_ONLY_STRONG_FOR_SERIALIZATION);
 }
 
 void StartupSerializer::VisitPointers(Object** start, Object** end) {
   if (start == isolate()->heap()->roots_array_start()) {
     // Serializing the root list needs special handling:
     // - The first pass over the root list only serializes immortal immovables.
     // - The second pass over the root list serializes the rest.
     // - Only root list elements that have been fully serialized can be
@@ skipping 26 matching lines @@
   if (root_index == Heap::kStackLimitRootIndex ||
       root_index == Heap::kRealStackLimitRootIndex) {
     return true;
   }
   return Heap::RootIsImmortalImmovable(root_index) !=
          serializing_immortal_immovables_roots_;
 }
 
 }  // namespace internal
 }  // namespace v8