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

Source/core/workers/WorkerIsolateWrapper.h

Index: Source/core/workers/WorkerIsolateWrapper.h
diff --git a/Source/core/workers/WorkerIsolateWrapper.h b/Source/core/workers/WorkerIsolateWrapper.h
new file mode 100644
index 0000000000000000000000000000000000000000..f3d2f22e1f71c32ceffc7d38d12aeb73dbcc72d8
--- /dev/null
+++ b/Source/core/workers/WorkerIsolateWrapper.h
@@ -0,0 +1,36 @@
+// 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.
+
+#ifndef WorkerIsolateWrapper_h
+#define WorkerIsolateWrapper_h
+
+#include "core/CoreExport.h"
+#include "wtf/OwnPtr.h"
+#include "wtf/PassOwnPtr.h"
+#include <v8.h>
+
+namespace blink {
+
+// A common interface for a worker to manage the v8::Isolate used for the worker. Each
+// WorkerThread creates and owns an instance of WorkerIsolateWrapper. It is created and
+// destroyed in the worker thread. A WorkerIsolateWrapper instance may create and own its
+// own v8::Isolate (the default implementation). But it is also possible for the
+// implementation to share the v8::Isolate with other WorkerIsolateWrapper instances in
+// the same thread.
+class CORE_EXPORT WorkerIsolateWrapper {
+public:
+    static PassOwnPtr<WorkerIsolateWrapper> createDefault();
+    virtual ~WorkerIsolateWrapper() { }
+
+    virtual v8::Isolate* isolate() const = 0;
+    virtual void willDestroy() = 0;
+    virtual void terminateExecution() = 0;
+
+protected:
+    WorkerIsolateWrapper() { }
+};
+
+} // namespace blink
+
+#endif // WorkerIsolateWrapper_h