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

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1830 matching lines @@
   }
 
   void UpdateTotalGCTime(double duration);
 
   bool MaximumSizeScavenge() { return maximum_size_scavenges_ > 0; }
 
   // ===========================================================================
   // Growing strategy. =========================================================
   // ===========================================================================
 
+  // 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,
                                           double mutator_speed);
 
   // Calculates the allocation limit based on a given growing factor and a
   // given old generation size.
   size_t CalculateOldGenerationAllocationLimit(double factor,
                                                size_t old_gen_size);
 
@@ skipping 805 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_