Fix %GetWeakSetValues to work correctly with GC.

src/runtime/runtime-collections.cc

Index: src/runtime/runtime-collections.cc
diff --git a/src/runtime/runtime-collections.cc b/src/runtime/runtime-collections.cc
index e6a86d114a7f8d04828f0c049deaa93bc3c14491..abdd056998e70f5903d887789f9a4ca40b2258a4 100644
--- a/src/runtime/runtime-collections.cc
+++ b/src/runtime/runtime-collections.cc
@@ -394,6 +394,10 @@ RUNTIME_FUNCTION(Runtime_GetWeakSetValues) {
     max_values = table->NumberOfElements();
   }
   Handle<FixedArray> values = isolate->factory()->NewFixedArray(max_values);
+  // Recompute max_values because GC could have removed elements from the table.
+  if (max_values > table->NumberOfElements()) {
+    max_values = table->NumberOfElements();
+  }
   {
     DisallowHeapAllocation no_gc;
     int count = 0;