Don't clear adoptedStyleSheets when moving shadow root between document <-> template
As discussed in https://github.com/WICG/construct-stylesheets/issues/133,
it should be safe to keep the adoptedStyleSheets when the shadow root
is moved between a document and a <template> within that document. We
should still clear the adoptedStyleSheets when moving a shadow root
between documents outside of that case (e.g. between iframes).
I2S: https://groups.google.com/a/chromium.org/g/blink-dev/c/W5-EGUySQgc/m/HxrySSpsBAAJ
Bug: 1111864
Change-Id: I803e75e6339f9228289188e4ed7d3f14c6e2432c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2464519
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822999}
diff --git a/css/cssom/CSSStyleSheet-template-adoption.html b/css/cssom/CSSStyleSheet-template-adoption.html
new file mode 100644
index 0000000..8fecbd8
--- /dev/null
+++ b/css/cssom/CSSStyleSheet-template-adoption.html
@@ -0,0 +1,47 @@
+<!doctype html>
+<title>adoptedStyleSheets should stay when adopting to/from template document</title>
+<link rel="author" title="Rakina Zata Amni" href="mailto:rakina@chromium.org">
+<link rel="help" href="https://wicg.github.io/construct-stylesheets/">
+<script src = '/resources/testharness.js'></script>
+<script src = '/resources/testharnessreport.js'></script>
+<body>
+<div id="host"></div>
+<template id='template'>
+ <template id='nested_template'></template>
+</template>
+</body>
+<script>
+test(function() {
+ let sheet = new CSSStyleSheet();
+ sheet.replaceSync("div { color: red }");
+
+ let host = document.getElementById("host");
+ let root = host.attachShadow({ mode: "open" });
+ root.adoptedStyleSheets = [sheet];
+ assert_equals(root.adoptedStyleSheets.length, 1);
+ assert_equals(root.adoptedStyleSheets[0], sheet);
+
+ // adoptedStyleSheets is not cleared when adopted into a <template>.
+ const template = document.getElementById("template");
+ template.content.appendChild(host);
+ assert_equals(root.adoptedStyleSheets.length, 1);
+ assert_equals(root.adoptedStyleSheets[0], sheet);
+
+ // adoptedStyleSheets is not cleared when adopted back in the main document.
+ document.body.appendChild(host);
+ assert_equals(root.adoptedStyleSheets.length, 1);
+ assert_equals(root.adoptedStyleSheets[0], sheet);
+
+ // adoptedStyleSheets is not cleared when adopted into a nested <template>.
+ const nested_template = template.content.firstElementChild;
+ nested_template.content.appendChild(host);
+ assert_equals(root.adoptedStyleSheets.length, 1);
+ assert_equals(root.adoptedStyleSheets[0], sheet);
+
+ // adoptedStyleSheets is cleared when adopted into an <iframe>.
+ const iframe = document.createElement("iframe");
+ document.body.appendChild(iframe);
+ iframe.contentDocument.body.appendChild(host);
+ assert_equals(root.adoptedStyleSheets.length, 0);
+}, "adoptedStyleSheets won'te be cleared when adopting into/from <template>s");
+</script>
