Fix test: manually call GC since 0 allocations will not cause GC

test/cctest/test-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 2843 matching lines @@
   AddTransitions(transitions_count);
   CompileRun("var root = new F;");
   Handle<JSObject> root = GetByName("root");
 
   // Count number of live transitions before marking.
   int transitions_before = CountMapTransitions(root->map());
   CHECK_EQ(transitions_count, transitions_before);
 
   root = GetByName("root");
   AddPropertyTo(0, root, "prop9");
+  CcTest::i_isolate()->heap()->CollectGarbage(OLD_POINTER_SPACE);
 
   // Count number of live transitions after marking.  Note that one transition
   // is left, because 'o' still holds an instance of one transition target.
   int transitions_after = CountMapTransitions(
       Map::cast(root->map()->GetBackPointer()));
   CHECK_EQ(1, transitions_after);
 }
 
 
 TEST(TransitionArraySimpleToFull) {
@@ skipping 1633 matching lines @@
 #ifdef DEBUG
 TEST(PathTracer) {
   CcTest::InitializeVM();
   v8::HandleScope scope(CcTest::isolate());
 
   v8::Local<v8::Value> result = CompileRun("'abc'");
   Handle<Object> o = v8::Utils::OpenHandle(*result);
   CcTest::i_isolate()->heap()->TracePathToObject(*o);
 }
 #endif  // DEBUG