[heap] Add --lazy-new-space-shrinking flag and configure the initial heap accordingly.

Bug: chromium:1054771
Change-Id: Id6fa131187caf67b2d7dddca548c2864ac5afaac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2260565Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68488}

src/flags/flag-definitions.h

@@ -830,6 +830,8 @@ DEFINE_INT(stress_sampling_allocation_profiler, 0,
            "Enables sampling allocation profiler with X as a sample interval")
 
 // Garbage collections flags.
+DEFINE_BOOL(lazy_new_space_shrinking, false,
+            "Enables the lazy new space shrinking strategy")
 DEFINE_SIZE_T(min_semi_space_size, 0,
               "min size of a semi-space (in MBytes), the new space consists of "
               "two semi-spaces")

src/heap/heap.cc

@@ -4772,6 +4772,10 @@ void Heap::ConfigureHeap(const v8::ResourceConstraints& constraints) {
         RoundDown<Page::kPageSize>(initial_semispace_size_);
   }
 
+  if (FLAG_lazy_new_space_shrinking) {
+    initial_semispace_size_ = max_semi_space_size_;
+  }
+
   // Initialize initial_old_space_size_.
   {
     initial_old_generation_size_ = kMaxInitialOldGenerationSize;