[heap] Add --stress-incremental-marking flag.

test/cctest/test-heap-profiler.cc

 // Copyright 2011 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 2012 matching lines @@
   data.GetParameter()->Reset();
 }
 
 
 TEST(WeakGlobalHandle) {
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());
 
   CHECK(!HasWeakGlobalHandle());
 
-  v8::Persistent<v8::Object> handle(env->GetIsolate(),
-                                    v8::Object::New(env->GetIsolate()));
+  v8::Persistent<v8::Object> handle;
+
+  handle.Reset(env->GetIsolate(), v8::Object::New(env->GetIsolate()));
   handle.SetWeak(&handle, PersistentHandleCallback,
                  v8::WeakCallbackType::kParameter);
 
   CHECK(HasWeakGlobalHandle());
+  CcTest::CollectAllGarbage();
+  EmptyMessageQueues(env->GetIsolate());
 }
 
 
 TEST(SfiAndJsFunctionWeakRefs) {
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());
   v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
 
   CompileRun(
       "fun = (function (x) { return function () { return x + 1; } })(1);");
@@ skipping 908 matching lines @@
       "      a[i] = i;\n"
       "  for (var i = 0; i < 3; ++i)\n"
       "      a.shift();\n"
       "}\n");
 
   CcTest::CollectGarbage(v8::internal::NEW_SPACE);
   // Should not crash.
 
   heap_profiler->StopSamplingHeapProfiler();
 }