[heap] Reland "Use RAIL mode for initial heap sizing"

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index e95dd2965ba708eabe6c6fbd18b0a13d6c0adce2..b1015c01e0a0f25c84ad12d4a1d3c066a29fbb08 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -5304,6 +5304,13 @@ void Heap::DampenOldGenerationAllocationLimit(size_t old_gen_size,
   }
 }
 
+bool Heap::ShouldOptimizeForLoadTime() {
+  return isolate()->rail_mode() == PERFORMANCE_LOAD &&
+         PromotedTotalSize() < initial_old_generation_size_ &&
+         MonotonicallyIncreasingTimeInMs() <
+             isolate()->LoadStartTimeMs() + kMaxLoadTimeMs;
+}
+
 // This predicate is called when an old generation space cannot allocated from
 // the free list and is about to add a new page. Returning false will cause a
 // major GC. It happens when the old generation allocation limit is reached and
@@ -5315,6 +5322,8 @@ bool Heap::ShouldExpandOldGenerationOnSlowAllocation() {
 
   if (ShouldOptimizeForMemoryUsage()) return false;
 
+  if (ShouldOptimizeForLoadTime()) return true;
+
   if (incremental_marking()->NeedsFinalization()) {
     return !AllocationLimitOvershotByLargeMargin();
   }