Bug 1487649 - Don't do a name check when cloning a shadow root for print preview. r=smaug

Otherwise the ShadowRoot for <use> or other internal ones may not get cloned
properly.

Differential Revision: https://phabricator.services.mozilla.com/D4756

--HG--
extra : moz-landing-system : lando

dom/base/nsNodeUtils.cpp

@@ -610,13 +610,8 @@ nsNodeUtils::CloneAndAdopt(nsINode *aNode, bool aClone, bool aDeep,
       if (clone->OwnerDoc()->IsStaticDocument()) {
         ShadowRoot* originalShadowRoot = aNode->AsElement()->GetShadowRoot();
         if (originalShadowRoot) {
-          ShadowRootInit init;
-          init.mMode = originalShadowRoot->Mode();
           RefPtr<ShadowRoot> newShadowRoot =
-            clone->AsElement()->AttachShadow(init, aError);
-          if (NS_WARN_IF(aError.Failed())) {
-            return nullptr;
-          }
+            clone->AsElement()->AttachShadowWithoutNameChecks(originalShadowRoot->Mode());
 
           newShadowRoot->CloneInternalDataFrom(originalShadowRoot);
           for (nsIContent* origChild = originalShadowRoot->GetFirstChild();

layout/base/tests/chrome/printpreview_helper.xul

@@ -306,6 +306,41 @@ async function runTest8() {
   exitprintpreview();
   ok(compareCanvases(), "Printing pages with fonts loaded from CSS and JS should be the same.");
 
+  requestAnimationFrame(function() { setTimeout(runTest9); } );
+}
+
+// Test for bug 1487649
+async function runTest9() {
+  window.frames[0].document.body.innerHTML = `
+    <svg width="100" height="100">
+      <rect width='100' height='100' fill='lime'/>
+    </svg>
+  `;
+
+  printpreview();
+  ctx1.drawWindow(window.frames[1], 0, 0, 400, 400, "rgb(255,255,255)");
+  exitprintpreview();
+
+  window.frames[0].document.body.innerHTML = `
+    <svg width="100" height="100">
+      <defs>
+        <g id="useme">
+          <rect width='100' height='100' fill='lime'/>
+        </g>
+      </defs>
+      <use href="#useme" />
+    </svg>
+  `;
+
+  // Ensure the <use> shadow tree is created so we test what we want to test.
+  await new Promise(resolve => requestAnimationFrame(resolve));
+  await new Promise(resolve => requestAnimationFrame(resolve));
+
+  printpreview();
+  ctx2.drawWindow(window.frames[1], 0, 0, 400, 400, "rgb(255,255,255)");
+  exitprintpreview();
+  ok(compareCanvases(), "Printing <use> subtrees should create same output");
+
   finish();
 }