Notify listeners on OffScreenCanvas changes

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 68d1351e64a3af40a74ff91a8bf00eac10f2c91e..b151a05b6358240e96214c5129f3a4d650dff5f0 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -1337,6 +1337,17 @@ ScriptPromise HTMLCanvasElement::createImageBitmap(
       isPaintable() ? ImageBitmap::create(this, cropRect, options) : nullptr);
 }
 
+void HTMLCanvasElement::setPlaceholderFrame(
+    RefPtr<StaticBitmapImage> image,
+    WeakPtr<OffscreenCanvasFrameDispatcher> dispatcher,
+    RefPtr<WebTaskRunner> taskRunner,
+    unsigned resourceId) {
+  OffscreenCanvasPlaceholder::setPlaceholderFrame(
+      std::move(image), std::move(dispatcher), std::move(taskRunner),
+      resourceId);
+  notifyListenersCanvasChanged();
+}
+
 bool HTMLCanvasElement::isOpaque() const {
   return m_context && !m_context->creationAttributes().alpha();
 }