Indicate that low-memory-notificatin triggered GCs are "forced"

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 779 matching lines @@
     DisallowHeapAllocation no_recursive_gc;
     isolate()->optimizing_compile_dispatcher()->Flush();
   }
   isolate()->ClearSerializerData();
   mark_compact_collector()->SetFlags(kMakeHeapIterableMask |
                                      kReduceMemoryFootprintMask);
   isolate_->compilation_cache()->Clear();
   const int kMaxNumberOfAttempts = 7;
   const int kMinNumberOfAttempts = 2;
   for (int attempt = 0; attempt < kMaxNumberOfAttempts; attempt++) {
-    if (!CollectGarbage(MARK_COMPACTOR, gc_reason, NULL) &&
+    if (!CollectGarbage(MARK_COMPACTOR, gc_reason, NULL,
+                        v8::kGCCallbackFlagForced) &&
         attempt + 1 >= kMinNumberOfAttempts) {
       break;
     }
   }
   mark_compact_collector()->SetFlags(kNoGCFlags);
   new_space_.Shrink();
   UncommitFromSpace();
 }
 
 
@@ skipping 5593 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal