Slow down incremental marking on main thread when idle notification is active.

BUG=

Review URL: https://codereview.chromium.org/771703004

Cr-Commit-Position: refs/heads/master@{#25630}

src/heap/heap.cc

@@ -120,6 +120,7 @@ Heap::Heap()
       min_in_mutator_(kMaxInt),
       marking_time_(0.0),
       sweeping_time_(0.0),
+      last_idle_notification_time_(0.0),
       mark_compact_collector_(this),
       store_buffer_(this),
       marking_(this),
@@ -4530,6 +4531,7 @@ bool Heap::IdleNotification(double deadline_in_seconds) {
   }
 
   double current_time = MonotonicallyIncreasingTimeInMs();
+  last_idle_notification_time_ = current_time;
   double deadline_difference = deadline_in_ms - current_time;
 
   if (deadline_difference >= 0) {
@@ -4564,6 +4566,13 @@ bool Heap::IdleNotification(double deadline_in_seconds) {
 }
 
 
+bool Heap::RecentIdleNotifcationHappened() {
+  return (last_idle_notification_time_ +
+          GCIdleTimeHandler::kMaxFrameRenderingIdleTime) >
+         MonotonicallyIncreasingTimeInMs();
+}
+
+
 #ifdef DEBUG
 
 void Heap::Print() {

src/heap/heap.h

@@ -1295,6 +1295,8 @@ class Heap {
 
   int gc_count() const { return gc_count_; }
 
+  bool RecentIdleNotifcationHappened();
+
   // Completely clear the Instanceof cache (to stop it keeping objects alive
   // around a GC).
   inline void CompletelyClearInstanceofCache();
@@ -2057,6 +2059,9 @@ class Heap {
   // Cumulative GC time spent in sweeping
   double sweeping_time_;
 
+  // Last time an idle notification happened
+  double last_idle_notification_time_;
+
   MarkCompactCollector mark_compact_collector_;
 
   StoreBuffer store_buffer_;

src/heap/incremental-marking.cc

@@ -880,6 +880,12 @@ intptr_t IncrementalMarking::Step(intptr_t allocated_bytes,
     return 0;
   }
 
+  // If an idle notification happened recently, we delay marking steps.
+  if (marking == DO_NOT_FORCE_MARKING &&
+      heap_->RecentIdleNotifcationHappened()) {
+    return 0;
+  }
+
   if (state_ == MARKING && no_marking_scope_depth_ > 0) return 0;
 
   intptr_t bytes_processed = 0;