[compositorworker] Avoid deadlock issue caused by importScript

third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js

Index: third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js
diff --git a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js
index b4d3a2ba97da2bf8c04d230a22d1d7a3d49648d1..8eef06661ace7e1afa5d7932e0861a247b2d1746 100644
--- a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/visual-update.js
@@ -1,5 +1,3 @@
-self.importScripts('worker-common.js');
-
 self.onmessage = function(msg) {
   awaitProxyInit(msg.data.proxy).then((proxy) => {
     proxy.opacity = 0.5;
@@ -11,3 +9,14 @@ self.onmessage = function(msg) {
     postMessage({});
   });
 }
+
+function awaitProxyInit(proxy) {
+  return new Promise((resolve, reject) => {
+    function check() {
+      if (proxy.initialized)
+        resolve(proxy);
+      requestAnimationFrame(check);
+    }
+    requestAnimationFrame(check);
+  });
+}