[heap] Use RAIL mode for initial heap sizing

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 9e63c5dc35e7497a88ae8c8c4daa4a075ba46e5d..878f41dc14aa50bc51eb719c6db5ca57e285996f 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -581,8 +581,6 @@ class Heap {
   };
   typedef List<Chunk> Reservation;
 
-  static const int kInitalOldGenerationLimitFactor = 2;
-
 #if V8_OS_ANDROID
   // Don't apply pointer multiplier on Android since it has no swap space and
   // should instead adapt it's heap size based on available physical memory.
@@ -1721,8 +1719,6 @@ class Heap {
   // Flush the number to string cache.
   void FlushNumberStringCache();
 
-  void ConfigureInitialOldGenerationSize();
-
   bool HasLowYoungGenerationAllocationRate();
   bool HasLowOldGenerationAllocationRate();
   double YoungGenerationMutatorUtilization();
@@ -1813,11 +1809,7 @@ class Heap {
   // GC statistics. ============================================================
   // ===========================================================================
 
-  inline size_t OldGenerationSpaceAvailable() {
-    if (old_generation_allocation_limit_ <= PromotedTotalSize()) return 0;
-    return old_generation_allocation_limit_ -
-           static_cast<size_t>(PromotedTotalSize());
-  }
+  size_t OldGenerationSpaceAvailable();
 
   void UpdateTotalGCTime(double duration);
 
@@ -1827,6 +1819,16 @@ class Heap {
   // Growing strategy. =========================================================
   // ===========================================================================
 
+  static const int kInitalOldGenerationLimitFactor = 2;
+
+  // For some webpages RAIL mode does not switch from PERFORMANCE_LOAD.
+  // This constant limits the effect of load RAIL mode on GC.
+  // The value is arbitrary and chosen as the largest load time observed in
+  // v8 browsing benchmarks.
+  static const int kMaxLoadTimeMs = 3000;
+
+  bool ShouldOptimizeForLoadTime();
+
   // Decrease the allocation limit if the new limit based on the given
   // parameters is lower than the current limit.
   void DampenOldGenerationAllocationLimit(size_t old_gen_size, double gc_speed,
@@ -2116,7 +2118,6 @@ class Heap {
   size_t initial_semispace_size_;
   size_t max_old_generation_size_;
   size_t initial_old_generation_size_;
-  bool old_generation_size_configured_;
   size_t max_executable_size_;
   size_t maximum_committed_;