Make full GC reduce memory footprint an explicit event in the idle notification handler.

src/heap/gc-idle-time-handler.cc

Index: src/heap/gc-idle-time-handler.cc
diff --git a/src/heap/gc-idle-time-handler.cc b/src/heap/gc-idle-time-handler.cc
index a3383b9c0c0dcde34864a7fbbafef853d24d5d55..5d12ac21bea9e0cbc3891bdd9a3b24272d1ab8a7 100644
--- a/src/heap/gc-idle-time-handler.cc
+++ b/src/heap/gc-idle-time-handler.cc
@@ -39,6 +39,9 @@ void GCIdleTimeAction::Print() {
     case DO_FULL_GC:
       PrintF("full GC");
       break;
+    case DO_FULL_GC_COMPACT:
+      PrintF("full GC compact");
+      break;
     case DO_FINALIZE_SWEEPING:
       PrintF("finalize sweeping");
       break;
@@ -156,10 +159,15 @@ bool GCIdleTimeHandler::ShouldDoScavenge(
 bool GCIdleTimeHandler::ShouldDoMarkCompact(
     size_t idle_time_in_ms, size_t size_of_objects,
     size_t mark_compact_speed_in_bytes_per_ms) {
-  return idle_time_in_ms >= kMaxScheduledIdleTime &&
-         idle_time_in_ms >=
-             EstimateMarkCompactTime(size_of_objects,
-                                     mark_compact_speed_in_bytes_per_ms);
+  return idle_time_in_ms >=
+         EstimateMarkCompactTime(size_of_objects,
+                                 mark_compact_speed_in_bytes_per_ms);
+}
+
+
+bool GCIdleTimeHandler::ShouldDoReduceMemoryMarkCompact(
+    size_t idle_time_in_ms) {
+  return idle_time_in_ms >= kMinTimeForReduceMemory;
 }
 
 
@@ -207,13 +215,14 @@ GCIdleTimeAction GCIdleTimeHandler::NothingOrDone() {
 // (3) If there is currently no MarkCompact idle round going on, we start a
 // new idle round if enough garbage was created. Otherwise we do not perform
 // garbage collection to keep system utilization low.
-// (4) If incremental marking is done, we perform a full garbage collection
-// if  we are allowed to still do full garbage collections during this idle
+// (4) If we have long idle time, we try to reduce the memory footprint.
+// (5) If incremental marking is done, we perform a full garbage collection
+// if we are allowed to still do full garbage collections during this idle
 // round or if we are not allowed to start incremental marking. Otherwise we
 // do not perform garbage collection to keep system utilization low.
-// (5) If sweeping is in progress and we received a large enough idle time
+// (6) If sweeping is in progress and we received a large enough idle time
 // request, we finalize sweeping here.
-// (6) If incremental marking is in progress, we perform a marking step. Note,
+// (7) If incremental marking is in progress, we perform a marking step. Note,
 // that this currently may trigger a full garbage collection.
 GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
                                             HeapState heap_state) {
@@ -247,6 +256,10 @@ GCIdleTimeAction GCIdleTimeHandler::Compute(double idle_time_in_ms,
     }
   }
 
+  if (ShouldDoReduceMemoryMarkCompact(static_cast<size_t>(idle_time_in_ms))) {
+    return GCIdleTimeAction::FullGCCompact();
+  }
+
   if (heap_state.incremental_marking_stopped) {
     if (ShouldDoMarkCompact(static_cast<size_t>(idle_time_in_ms),
                             heap_state.size_of_objects,