Add the rate of js invocations from the api as a signal of idleness

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 217ac0123eb3e96040cebb2ebfd358d197922285..cc384d353e9379a5aa7d5c555da67d22b43cf29b 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -35,6 +35,7 @@
 #include "src/factory.h"
 #include "src/global-handles.h"
 #include "src/heap/gc-tracer.h"
+#include "src/heap/memory-reducer.h"
 #include "src/ic/ic.h"
 #include "src/macro-assembler.h"
 #include "src/snapshot/snapshot.h"
@@ -6274,5 +6275,30 @@ TEST(Regress519319) {
 }
 
 
+HEAP_TEST(TestMemoryReducerSampleJsCalls) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+  Heap* heap = CcTest::heap();
+  Isolate* isolate = CcTest::i_isolate();
+  MemoryReducer* memory_reducer = heap->memory_reducer_;
+  memory_reducer->SampleAndGetJsCallsPerMs(0);
+  isolate->IncrementJsCallsFromApiCounter();
+  isolate->IncrementJsCallsFromApiCounter();
+  isolate->IncrementJsCallsFromApiCounter();
+  double calls_per_ms = memory_reducer->SampleAndGetJsCallsPerMs(1);
+  CheckDoubleEquals(3, calls_per_ms);
+
+  calls_per_ms = memory_reducer->SampleAndGetJsCallsPerMs(2);
+  CheckDoubleEquals(0, calls_per_ms);
+
+  isolate->IncrementJsCallsFromApiCounter();
+  isolate->IncrementJsCallsFromApiCounter();
+  isolate->IncrementJsCallsFromApiCounter();
+  isolate->IncrementJsCallsFromApiCounter();
+  calls_per_ms = memory_reducer->SampleAndGetJsCallsPerMs(4);
+  CheckDoubleEquals(2, calls_per_ms);
+}
+
+
 }  // namespace internal
 }  // namespace v8