Replace reduce-memory mode in idle notification with delayed clean-up GC.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index a57a46d85edd6c351bc66be96d192271b6be3578..f32e88d1bde4d305340bc9b61a4b2917980dfaa3 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -16,6 +16,7 @@
 #include "src/heap/gc-tracer.h"
 #include "src/heap/incremental-marking.h"
 #include "src/heap/mark-compact.h"
+#include "src/heap/memory-reducer.h"
 #include "src/heap/objects-visiting.h"
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
@@ -831,6 +832,10 @@ class Heap {
   // Notify the heap that a context has been disposed.
   int NotifyContextDisposed(bool dependant_context);
 
+  // Start incremental marking and ensure that idle time handler can perform
+  // incremental steps.
+  void StartIdleIncrementalMarking();
+
   inline void increment_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_++;
     if (FLAG_gc_verbose) {
@@ -1613,6 +1618,10 @@ class Heap {
   // An ArrayBuffer moved from new space to old space.
   void PromoteArrayBuffer(Object* buffer);
 
+  bool HasLowAllocationRate();
+  bool HasHighFragmentation();
+  bool HasHighFragmentation(intptr_t used, intptr_t committed);
+
  protected:
   // Methods made available to tests.
 
@@ -1773,10 +1782,6 @@ class Heap {
   // generation and on every allocation in large object space.
   intptr_t old_generation_allocation_limit_;
 
-  // The allocation limit when there is >16.66ms idle time in the idle time
-  // handler.
-  intptr_t idle_old_generation_allocation_limit_;
-
   // Indicates that an allocation has failed in the old generation since the
   // last GC.
   bool old_gen_exhausted_;
@@ -2251,7 +2256,6 @@ class Heap {
 
   bool HasLowYoungGenerationAllocationRate();
   bool HasLowOldGenerationAllocationRate();
-  bool HasLowAllocationRate();
 
   void ReduceNewSpaceSize();
 
@@ -2318,6 +2322,8 @@ class Heap {
 
   GCIdleTimeHandler gc_idle_time_handler_;
 
+  MemoryReducer memory_reducer_;
+
   // These two counters are monotomically increasing and never reset.
   size_t full_codegen_bytes_generated_;
   size_t crankshaft_codegen_bytes_generated_;