Memory reducer should use the current allocation rate instead of the overall allocation rate.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 6dc67fcffe69b91183035911750c3356141d4229..1cb3ce82697b245e1718dfd036b8bfe239c574b3 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -4757,7 +4757,7 @@ static double ComputeMutatorUtilization(double mutator_speed, double gc_speed) {
 
 double Heap::YoungGenerationMutatorUtilization() {
   double mutator_speed = static_cast<double>(
-      tracer()->NewSpaceAllocationThroughputInBytesPerMillisecond());
+      tracer()->CurrentNewSpaceAllocationThroughputInBytesPerMillisecond());
   double gc_speed = static_cast<double>(
       tracer()->ScavengeSpeedInBytesPerMillisecond(kForSurvivedObjects));
   double result = ComputeMutatorUtilization(mutator_speed, gc_speed);
@@ -4773,7 +4773,8 @@ double Heap::YoungGenerationMutatorUtilization() {
 
 double Heap::OldGenerationMutatorUtilization() {
   double mutator_speed = static_cast<double>(
-      tracer()->OldGenerationAllocationThroughputInBytesPerMillisecond());
+      tracer()
+          ->CurrentOldGenerationAllocationThroughputInBytesPerMillisecond());
   double gc_speed = static_cast<double>(
       tracer()->CombinedMarkCompactSpeedInBytesPerMillisecond());
   double result = ComputeMutatorUtilization(mutator_speed, gc_speed);