compositor-worker: Share a thread and an isolate for compositor workers.

Source/core/workers/WorkerThread.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 200 matching lines @@
 
         // The worker was terminated before the thread had a chance to run.
         if (m_terminated) {
             // Notify the proxy that the WorkerGlobalScope has been disposed of.
             // This can free this thread object, hence it must not be touched afterwards.
             m_workerReportingProxy.workerThreadTerminated();
             return;
         }
 
         m_microtaskRunner = adoptPtr(new WorkerMicrotaskRunner(this));
+        initializeBackingThread();
         backingThread().addTaskObserver(m_microtaskRunner.get());
-        backingThread().initialize();
 
         m_isolate = initializeIsolate();
         m_workerGlobalScope = createWorkerGlobalScope(startupData);
         m_workerGlobalScope->scriptLoaded(sourceCode.length(), cachedMetaData.get() ? cachedMetaData->size() : 0);
     }
     m_webScheduler = backingThread().platformThread().scheduler();
 
     // The corresponding call to stopRunLoop() is in ~WorkerScriptController().
     didStartRunLoop();
 
@@ skipping 33 matching lines @@
     // The below assignment will destroy the context, which will in turn notify messaging proxy.
     // We cannot let any objects survive past thread exit, because no other thread will run GC or otherwise destroy them.
     // If Oilpan is enabled, we detach of the context/global scope, with the final heap cleanup below sweeping it out.
 #if !ENABLE(OILPAN)
     ASSERT(m_workerGlobalScope->hasOneRef());
 #endif
     m_workerGlobalScope->notifyContextDestroyed();
     m_workerGlobalScope = nullptr;
 
     backingThread().removeTaskObserver(m_microtaskRunner.get());
-    backingThread().shutdown();
+    shutdownBackingThread();
     destroyIsolate();
+    m_isolate = nullptr;
 
     m_microtaskRunner = nullptr;
 
     // Notify the proxy that the WorkerGlobalScope has been disposed of.
     // This can free this thread object, hence it must not be touched afterwards.
     workerReportingProxy().workerThreadTerminated();
 
     m_terminationEvent->signal();
 }
 
@@ skipping 40 matching lines @@
     if (m_shutdown)
         return;
 
     // If the worker thread was never initialized, complete the termination immediately.
     if (!m_workerGlobalScope) {
         m_terminationEvent->signal();
         return;
     }
 
     // Ensure that tasks are being handled by thread event loop. If script execution weren't forbidden, a while(1) loop in JS could keep the thread alive forever.
+    m_workerGlobalScope->script()->willScheduleExecutionTermination();
     terminateV8Execution();
 
     InspectorInstrumentation::didKillAllExecutionContextTasks(m_workerGlobalScope.get());
     m_debuggerMessageQueue.kill();
     backingThread().postTask(FROM_HERE, new Task(threadSafeBind(&WorkerThread::shutdown, AllowCrossThreadAccess(this))));
 }
 
 void WorkerThread::didStartRunLoop()
 {
     ASSERT(isCurrentThread());
@@ skipping 49 matching lines @@
 void WorkerThread::postTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task)
 {
     backingThread().postTask(location, WorkerThreadTask::create(*this, task, true).leakPtr());
 }
 
 void WorkerThread::postDelayedTask(const WebTraceLocation& location, PassOwnPtr<ExecutionContextTask> task, long long delayMs)
 {
     backingThread().postDelayedTask(location, WorkerThreadTask::create(*this, task, true).leakPtr(), delayMs);
 }
 
+void WorkerThread::initializeBackingThread()
+{
+    ASSERT(isCurrentThread());
+    backingThread().initialize();
+}
+
+void WorkerThread::shutdownBackingThread()
+{
+    ASSERT(isCurrentThread());
+    backingThread().shutdown();
+}
+
 v8::Isolate* WorkerThread::initializeIsolate()
 {
     ASSERT(isCurrentThread());
     ASSERT(!m_isolate);
     v8::Isolate* isolate = V8PerIsolateData::initialize();
     V8Initializer::initializeWorker(isolate);
 
     m_interruptor = adoptPtr(new V8IsolateInterruptor(isolate));
     ThreadState::current()->addInterruptor(m_interruptor.get());
     ThreadState::current()->registerTraceDOMWrappers(isolate, V8GCController::traceDOMWrappers);
 
     return isolate;
 }
 
 void WorkerThread::willDestroyIsolate()
 {
     ASSERT(isCurrentThread());
     ASSERT(m_isolate);
     V8PerIsolateData::willBeDestroyed(m_isolate);
     ThreadState::current()->removeInterruptor(m_interruptor.get());
 }
 
 void WorkerThread::destroyIsolate()
 {
     ASSERT(isCurrentThread());
     V8PerIsolateData::destroy(m_isolate);
-    m_isolate = nullptr;
 }
 
 void WorkerThread::terminateV8Execution()
 {
     ASSERT(isMainThread());
-    m_workerGlobalScope->script()->willScheduleExecutionTermination();
     v8::V8::TerminateExecution(m_isolate);
 }
 
 void WorkerThread::appendDebuggerTask(PassOwnPtr<WebThread::Task> task)
 {
     m_debuggerMessageQueue.append(task);
 }
 
 MessageQueueWaitResult WorkerThread::runDebuggerTask(WaitMode waitMode)
 {
@@ skipping 27 matching lines @@
     InspectorInstrumentation::didLeaveNestedRunLoop(m_workerGlobalScope.get());
 }
 
 void WorkerThread::setWorkerInspectorController(WorkerInspectorController* workerInspectorController)
 {
     MutexLocker locker(m_workerInspectorControllerMutex);
     m_workerInspectorController = workerInspectorController;
 }
 
 } // namespace blink