Refactoring WorkletThreadBackingHolder with template pattern

third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h

Index: third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h
diff --git a/third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h b/third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h
index b976d6d0cd8e24977bb7fb450f64a3ea5b11163e..52ed15cba20f1f22b60e1ddd8abea2b42a0c98f3 100644
--- a/third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h
+++ b/third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h
@@ -21,20 +21,20 @@ class MODULES_EXPORT AbstractAnimationWorkletThread : public WorkerThread {
   ~AbstractAnimationWorkletThread() override;
 
   WorkerBackingThread& workerBackingThread() override;
-  void clearWorkerBackingThread() override {
-    // Do nothing.
-    // The backing thread is cleared by clearSharedBackingThread().
-  }
+
+  // The backing thread is cleared by clearSharedBackingThread().
+  void clearWorkerBackingThread() override {}
 
   bool shouldAttachThreadDebugger() const override { return false; }
 
+  // This may block the main thread.
   static void collectAllGarbage();
 
   static void ensureSharedBackingThread();
-  static void createSharedBackingThreadForTest();
-
   static void clearSharedBackingThread();
 
+  static void createSharedBackingThreadForTest();
+
  protected:
   AbstractAnimationWorkletThread(PassRefPtr<WorkerLoaderProxy>,
                                  WorkerReportingProxy&);