Hook up CSSPaintValue::image to CSS Paint API callback.

third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-worklet.js

Index: third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-worklet.js
diff --git a/third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-worklet.js b/third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-worklet.js
new file mode 100644
index 0000000000000000000000000000000000000000..323b6a39b4884411eae2700212c99cec8ae272e0
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/csspaint/resources/test-runner-paint-worklet.js
@@ -0,0 +1,20 @@
+// Given a piece of 'code', runs it in the worklet, then once loaded waits for
+// layout and paint, before finishing the test.
+//
+// Usage:
+//   importPaintWorkletAndTerminateTestAfterAsyncPaint('/* worklet code goes here. */');
+
+function importPaintWorkletAndTerminateTestAfterAsyncPaint(code) {
+    if (window.testRunner) {
+      testRunner.waitUntilDone();
+    }
+
+    var blob = new Blob([code]);
+    paintWorklet.import(URL.createObjectURL(blob)).then(function() {
+        runAfterLayoutAndPaint(function() {
+            if (window.testRunner) {
+                testRunner.notifyDone();
+            }
+        });
+    });
+}