HeapProfiler: integrate FindUntrackedObjects into js code.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 4b8865ab12914ce20a42286e39ea16fc536638b1..b614904c9f468ba08708c8a3bb96710598415ab2 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -280,6 +280,11 @@ static FixedArrayBase* LeftTrimFixedArray(Heap* heap,
     profiler->ObjectMoveEvent(elms->address(),
                               new_elms->address(),
                               new_elms->Size());
+    if (profiler->is_tracking_allocations()) {
+      // Report filler object as a new allocation.
+      // Otherwise it will become an untracked object.
+      profiler->NewObjectEvent(elms->address(), elms->Size());
+    }
   }
   return new_elms;
 }