[heap] Trigger scavenge jobs when new space is 80% full.

Bug: chromium:1056872
Change-Id: I68341f0320663796cd8487b66bb38d87c7ad8bd3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2115435Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66841}

src/heap/scavenge-job.cc

@@ -30,7 +30,7 @@ class ScavengeJob::Task : public CancelableTask {
 };
 
 size_t ScavengeJob::YoungGenerationTaskTriggerSize(Heap* heap) {
-  static constexpr double kTaskTriggerFactor = 0.618;
+  static constexpr double kTaskTriggerFactor = 0.8;
   return heap->new_space()->Capacity() * kTaskTriggerFactor;
 }