Uncommit and shrink semi-spaces only on low allocation rate.

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
diff --git a/test/cctest/test-heap.cc b/test/cctest/test-heap.cc
index d9d2a861ebf30d4644d91f71ee49ceaf10627f47..a37da264d498e1ef438e36f1c98ce36da109cb2a 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -5551,7 +5551,7 @@ TEST(NewSpaceAllocationThroughput2) {
   size_t counter2 = 2000;
   tracer->SampleNewSpaceAllocation(time2, counter2);
   size_t bytes = tracer->NewSpaceAllocatedBytesInLast(1000);
-  CHECK_EQ(0, bytes);
+  CHECK_EQ(10000, bytes);
   int time3 = 1000;
   size_t counter3 = 30000;
   tracer->SampleNewSpaceAllocation(time3, counter3);