Compute the heap growing factor based on mutator utilization and allocation throughput.

src/heap/gc-tracer.cc

Index: src/heap/gc-tracer.cc
diff --git a/src/heap/gc-tracer.cc b/src/heap/gc-tracer.cc
index 6ca724e5a1ef18158fa1b436f69ca5149df5ec80..f20e982c090bf72da42c419922c352bc5e683a0e 100644
--- a/src/heap/gc-tracer.cc
+++ b/src/heap/gc-tracer.cc
@@ -619,12 +619,12 @@ intptr_t GCTracer::FinalIncrementalMarkCompactSpeedInBytesPerMillisecond()
 double GCTracer::CombinedMarkCompactSpeedInBytesPerMillisecond() {
   if (combined_mark_compact_speed_cache_ > 0)
     return combined_mark_compact_speed_cache_;
-  const double kEpsilon = 1;
+  const double kMinimumMarkingSpeed = 0.5;
   double speed1 =
       static_cast<double>(IncrementalMarkingSpeedInBytesPerMillisecond());
   double speed2 = static_cast<double>(
       FinalIncrementalMarkCompactSpeedInBytesPerMillisecond());
-  if (speed1 + speed2 < kEpsilon) {
+  if (speed1 < kMinimumMarkingSpeed || speed2 < kMinimumMarkingSpeed) {
     // No data for the incremental marking speed.
     // Return the non-incremental mark-compact speed.
     combined_mark_compact_speed_cache_ =
@@ -685,9 +685,11 @@ size_t GCTracer::AllocationThroughputInBytesPerMillisecond(
 }
 
 
-size_t GCTracer::CurrentAllocationThroughputInBytesPerMillisecond() const {
+size_t GCTracer::CurrentOldGenerationAllocationThroughputInBytesPerMillisecond()
+    const {
   static const double kThroughputTimeFrame = 5000;
-  return AllocationThroughputInBytesPerMillisecond(kThroughputTimeFrame);
+  return OldGenerationAllocationThroughputInBytesPerMillisecond(
+      kThroughputTimeFrame);
 }