Revert "Allow incremental marking when expose_gc is turned on."

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5305 matching lines @@
       size_factor * IncrementalMarking::kAllocatedThreshold;
 
   if (contexts_disposed_ > 0) {
     if (hint >= kMaxHint) {
       // The embedder is requesting a lot of GC work after context disposal,
       // we age inline caches so that they don't keep objects from
       // the old context alive.
       AgeInlineCaches();
     }
     int mark_sweep_time = Min(TimeMarkSweepWouldTakeInMs(), 1000);
-    if (hint >= mark_sweep_time && incremental_marking()->IsStopped()) {
+    if (hint >= mark_sweep_time && !FLAG_expose_gc &&
+        incremental_marking()->IsStopped()) {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
       CollectAllGarbage(kReduceMemoryFootprintMask,
                         "idle notification: contexts disposed");
     } else {
       AdvanceIdleIncrementalMarking(step_size);
       contexts_disposed_ = 0;
     }
     // After context disposal there is likely a lot of garbage remaining, reset
     // the idle notification counters in order to trigger more incremental GCs
     // on subsequent idle notifications.
     StartIdleRound();
     return false;
   }
 
-  if (!FLAG_incremental_marking || Serializer::enabled()) {
+  if (!FLAG_incremental_marking || FLAG_expose_gc || Serializer::enabled()) {
     return IdleGlobalGC();
   }
 
   // By doing small chunks of GC work in each IdleNotification,
   // perform a round of incremental GCs and after that wait until
   // the mutator creates enough garbage to justify a new round.
   // An incremental GC progresses as follows:
   // 1. many incremental marking steps,
   // 2. one old space mark-sweep-compact,
   // 3. many lazy sweep steps.
@@ skipping 1977 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal