Bug 1827856 - Remove nativeAnonymousChildList observers. r=smaug,credential-management-reviewers,devtools-reviewers,sgalich,nchevobbe

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Differential Revision: https://phabricator.services.mozilla.com/D175382

layout/base/nsCSSFrameConstructor.cpp

@@ -1896,6 +1896,10 @@ void nsCSSFrameConstructor::CreateGeneratedContentItem(
     return;
   }
 
+  if (mDocument->DevToolsAnonymousAndShadowEventsEnabled()) {
+    container->QueueDevtoolsAnonymousEvent(/* aIsRemove = */ false);
+  }
+
   // Servo has already eagerly computed the style for the container, so we can
   // just stick the style on the element and avoid an additional traversal.
   //
@@ -3999,6 +4003,13 @@ nsresult nsCSSFrameConstructor::GetAnonymousContent(
     return rv;
   }
 
+  if (aContent.IsEmpty()) {
+    return NS_OK;
+  }
+
+  const bool devtoolsEventsEnabled =
+      mDocument->DevToolsAnonymousAndShadowEventsEnabled();
+
   MOZ_ASSERT(aParent->IsElement());
   for (const auto& info : aContent) {
     // get our child's content and set its parent to our content
@@ -4012,6 +4023,10 @@ nsresult nsCSSFrameConstructor::GetAnonymousContent(
       content->UnbindFromTree();
       return rv;
     }
+
+    if (devtoolsEventsEnabled) {
+      content->QueueDevtoolsAnonymousEvent(/* aIsRemove = */ false);
+    }
   }
 
   // Some situations where we don't cache anonymous content styles: