Disallow cross-thread Persistent<> read access.

third_party/WebKit/Source/core/loader/ThreadableLoaderTest.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/loader/ThreadableLoader.h"
 
 #include "core/dom/ExecutionContextTask.h"
 #include "core/loader/DocumentThreadableLoader.h"
 #include "core/loader/ThreadableLoaderClient.h"
 #include "core/loader/WorkerThreadableLoader.h"
@@ skipping 331 matching lines @@
       std::unique_ptr<WTF::CrossThreadClosure> task) override {
     DCHECK(m_workerThread);
     m_workerThread->postTask(location, std::move(task));
   }
 
   RefPtr<SecurityOrigin> m_securityOrigin;
   std::unique_ptr<MockWorkerReportingProxy> m_mockWorkerReportingProxy;
   std::unique_ptr<WorkerThreadForTest> m_workerThread;
 
   std::unique_ptr<DummyPageHolder> m_dummyPageHolder;
-  Persistent<ParentFrameTaskRunners> m_parentFrameTaskRunners;
+  // Accessed cross-thread when worker thread posts tasks to the parent.
+  CrossThreadPersistent<ParentFrameTaskRunners> m_parentFrameTaskRunners;
   Checkpoint m_checkpoint;
   // |m_loader| must be touched only from the worker thread only.
   CrossThreadPersistent<ThreadableLoader> m_loader;
 };
 
 class ThreadableLoaderTest
     : public ::testing::TestWithParam<ThreadableLoaderToTest> {
  public:
   ThreadableLoaderTest() {
     switch (GetParam()) {
@@ skipping 520 matching lines @@
   // test is not saying that didFailAccessControlCheck should be dispatched
   // synchronously, but is saying that even when a response is served
   // synchronously it should not lead to a crash.
   startLoader(KURL(KURL(), "about:blank"));
   callCheckpoint(2);
 }
 
 }  // namespace
 
 }  // namespace blink