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

Source/core/workers/WorkerThread.cpp

Index: Source/core/workers/WorkerThread.cpp
diff --git a/Source/core/workers/WorkerThread.cpp b/Source/core/workers/WorkerThread.cpp
index 883944ff2e4caeac2a8c5b0f951d687984b8da7e..6f3c60ec1d5555a2b07659681c6ea7709b7eb421 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -29,8 +29,6 @@
 #include "core/workers/WorkerThread.h"
 
 #include "bindings/core/v8/ScriptSourceCode.h"
-#include "bindings/core/v8/V8GCController.h"
-#include "bindings/core/v8/V8Initializer.h"
 #include "core/dom/Microtask.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/inspector/WorkerInspectorController.h"
@@ -316,7 +314,7 @@ void WorkerThread::initialize(PassOwnPtr<WorkerThreadStartupData> startupData)
 
         m_microtaskRunner = adoptPtr(new WorkerMicrotaskRunner(this));
         backingThread().addTaskObserver(m_microtaskRunner.get());
-        backingThread().initialize();
+        initializeBackingThread();
 
         m_isolate = initializeIsolate();
         m_workerGlobalScope = createWorkerGlobalScope(startupData);
@@ -373,7 +371,7 @@ void WorkerThread::shutdown()
     m_workerGlobalScope = nullptr;
 
     backingThread().removeTaskObserver(m_microtaskRunner.get());
-    backingThread().shutdown();
+    shutdownBackingThread();
     destroyIsolate();
 
     m_microtaskRunner = nullptr;
@@ -457,6 +455,16 @@ void WorkerThread::didStopRunLoop()
     Platform::current()->didStopWorkerRunLoop();
 }
 
+void WorkerThread::initializeBackingThread()
+{
+    backingThread().initialize();
+}
+
+void WorkerThread::shutdownBackingThread()
+{
+    backingThread().shutdown();
+}
+
 void WorkerThread::terminateAndWaitForAllWorkers()
 {
     // Keep this lock to prevent WorkerThread instances from being destroyed.
@@ -507,40 +515,31 @@ void WorkerThread::postDelayedTask(const WebTraceLocation& location, PassOwnPtr<
     backingThread().postDelayedTask(location, WorkerThreadTask::create(*this, task, true).leakPtr(), delayMs);
 }
 
-v8::Isolate* WorkerThread::initializeIsolate()
+PassOwnPtr<WorkerV8Isolate> 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;
+    return WorkerV8Isolate::createDefault();
 }
 
 void WorkerThread::willDestroyIsolate()
 {
     ASSERT(isCurrentThread());
     ASSERT(m_isolate);
-    V8PerIsolateData::willBeDestroyed(m_isolate);
-    ThreadState::current()->removeInterruptor(m_interruptor.get());
+    m_isolate->willDestroy();
 }
 
 void WorkerThread::destroyIsolate()
 {
     ASSERT(isCurrentThread());
-    V8PerIsolateData::destroy(m_isolate);
-    m_isolate = nullptr;
+    m_isolate.clear();
 }
 
 void WorkerThread::terminateV8Execution()
 {
     ASSERT(isMainThread());
     m_workerGlobalScope->script()->willScheduleExecutionTermination();
-    v8::V8::TerminateExecution(m_isolate);
+    m_isolate->terminateExecution();
 }
 
 void WorkerThread::appendDebuggerTask(PassOwnPtr<WebThread::Task> task)