[compositorworker] Avoid deadlock issue caused by importScript

third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js

Index: third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js
diff --git a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js
index 80fdfe9f99faf39d304bcf77eae8c976a2e3ca00..ea9234923f3e6f243a7afa6648c1e955b4f2b419 100644
--- a/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/fast/compositorworker/resources/basic-plumbing-worker-to-main.js
@@ -1,5 +1,3 @@
-self.importScripts('worker-common.js');
-
 self.onmessage = function(msg) {
   if (msg.data.proxy)
     self.proxy = msg.data.proxy;
@@ -15,3 +13,14 @@ self.onmessage = function(msg) {
     postMessage({});
   });
 }
+
+function awaitProxyInit(proxy) {
+  return new Promise((resolve, reject) => {
+    function check() {
+      if (proxy.initialized)
+        resolve(proxy);
+      requestAnimationFrame(check);
+    }
+    requestAnimationFrame(check);
+  });
+}