1 files changed, 45 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/embedded-content/resources/common.js b/testing/web-platform/tests/html/semantics/embedded-content/resources/common.js
new file mode 100644
index 0000000000..06f18b3e04
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/embedded-content/resources/common.js
@@ -0,0 +1,45 @@
+// Helper to access the element, its associated loading promise, and also to
+// resolve the promise.
+class ElementLoadPromise {
+  constructor(element_id) {
+    this.element_id = element_id;
+    this.promise = new Promise((resolve, reject) => {
+      this.resolve = resolve
+      this.reject = reject
+    });
+  }
+  element() {
+    return document.getElementById(this.element_id);
+  }
+}
+
+// Returns if the image is complete and the lazily loaded image matches the expected image.
+function is_image_fully_loaded(image, expected_image) {
+  if (!image.complete || !expected_image.complete) {
+    return false;
+  }
+
+  if (image.width != expected_image.width ||
+      image.height != expected_image.height) {
+    return false;
+  }
+
+  let canvas = document.createElement('canvas');
+  canvas.width = image.width;
+  canvas.height = image.height;
+  let canvasContext = canvas.getContext("2d");
+  canvasContext.save();
+  canvasContext.drawImage(image, 0, 0);
+  let data = canvasContext.getImageData(0, 0, canvas.width, canvas.height).data;
+
+  canvasContext.restore();
+  canvasContext.drawImage(expected_image, 0, 0);
+  let expected_data = canvasContext.getImageData(0, 0, canvas.width, canvas.height).data;
+
+  for (var i = 0; i < data.length; i++) {
+    if (data[i] != expected_data[i]) {
+      return false;
+    }
+  }
+  return true;
+}