compositor-worker: Keep worker backing thread alive for the lifetime of the compositor thread.

third_party/WebKit/Source/modules/compositorworker/CompositorWorkerThreadTest.cpp

 // Copyright 2015 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 "modules/compositorworker/CompositorWorkerThread.h"
 
 #include "bindings/core/v8/ScriptSourceCode.h"
 #include "bindings/core/v8/V8GCController.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/testing/DummyPageHolder.h"
@@ skipping 73 matching lines @@
     {
         CompositorWorkerThread::resetSharedBackingThreadForTest();
         m_page = DummyPageHolder::create();
         m_objectProxy = TestCompositorWorkerObjectProxy::create(&m_page->document());
         m_securityOrigin = SecurityOrigin::create(KURL(ParsedURLString, "http://fake.url/"));
     }
 
     void TearDown() override
     {
         m_page.clear();
-        CompositorWorkerThread::resetSharedBackingThreadForTest();
+        CompositorWorkerThread::clearSharedBackingThread();
     }
 
     PassOwnPtr<CompositorWorkerThread> createCompositorWorker()
     {
         OwnPtr<CompositorWorkerThread> workerThread = CompositorWorkerThread::create(nullptr, *m_objectProxy, 0);
         WorkerClients* clients = nullptr;
         workerThread->start(WorkerThreadStartupData::create(
             KURL(ParsedURLString, "http://fake.url/"),
             "fake user agent",
             "//fake source code",
@@ skipping 113 matching lines @@
     v8::Isolate* secondIsolate = secondWorker->isolate();
     ASSERT_TRUE(secondIsolate);
     EXPECT_EQ(firstIsolate, secondIsolate);
 
     // Verify that the isolate can run some scripts correctly in the second worker.
     checkWorkerCanExecuteScript(secondWorker.get());
     secondWorker->terminateAndWait();
 }
 
 } // namespace blink