[heap,snapshot] Replace first page size from snapshots with page trimming

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 545c0dde3d2f709daa99438e99cafe6534094084..a3da4c8eab08a9a63c795bf2b2cb9abe50d6dbfd 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2380,13 +2380,19 @@ bool Isolate::Init(Deserializer* des) {
   runtime_profiler_ = new RuntimeProfiler(this);
 
   // If we are deserializing, read the state into the now-empty heap.
-  if (!create_heap_objects) {
-    des->Deserialize(this);
-  }
-  load_stub_cache_->Initialize();
-  store_stub_cache_->Initialize();
-  if (FLAG_ignition || serializer_enabled()) {
-    interpreter_->Initialize();
+  {
+    AlwaysAllocateScope always_allocate(this);
+
+    if (!create_heap_objects) {
+      des->Deserialize(this);
+    }
+    load_stub_cache_->Initialize();
+    store_stub_cache_->Initialize();
+    if (FLAG_ignition || serializer_enabled()) {
+      interpreter_->Initialize();
+    }
+
+    heap_.NotifyDeserializationComplete();
   }
 
   // Finish initialization of ThreadLocal after deserialization is done.
@@ -2417,8 +2423,6 @@ bool Isolate::Init(Deserializer* des) {
 
   time_millis_at_init_ = heap_.MonotonicallyIncreasingTimeInMs();
 
-  heap_.NotifyDeserializationComplete();
-
   if (!create_heap_objects) {
     // Now that the heap is consistent, it's OK to generate the code for the
     // deopt entry table that might have been referred to by optimized code in