Print out how many AllocationMementos were found on a scavenge of new space

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 5d75cb46fdf9cfd8d2fbedda8c2ae29caa2dd3f2..5e89bdd968c9b523c8ff3b1ceb1709c10c2ab9ad 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -86,6 +86,7 @@ Heap::Heap()
       contexts_disposed_(0),
       global_ic_age_(0),
       flush_monomorphic_ics_(false),
+      allocation_mementos_found_on_scavenge_(0),
       scan_on_scavenge_pages_(0),
       new_space_(this),
       old_pointer_space_(NULL),
@@ -1328,6 +1329,8 @@ class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
 void Heap::Scavenge() {
   RelocationLock relocation_lock(this);
 
+  allocation_mementos_found_on_scavenge_ = 0;
+
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) VerifyNonPointerSpacePointers(this);
 #endif
@@ -1475,6 +1478,12 @@ void Heap::Scavenge() {
   gc_state_ = NOT_IN_GC;
 
   scavenges_since_last_idle_round_++;
+
+  if (FLAG_trace_track_allocation_sites &&
+      allocation_mementos_found_on_scavenge_ > 0) {
+    PrintF("AllocationMementos found during scavenge = %d\n",
+           allocation_mementos_found_on_scavenge_);
+  }
 }