Bug 1778345 - Align PerformanceEventTiming::GetAnElement with the spec r=emilio

There are two bugs in this function, first the function doesn't do
the `is not connected` check correctly as it supposes to use
`IsInComposed()` but rather `IsInUnComposed()`. Second, it
doesn't get the root of the element correctly.

Also this patch converts the function be static so that it can be
reused.

Differential Revision: https://phabricator.services.mozilla.com/D151081

dom/base/nsContentUtils.cpp

@@ -2538,6 +2538,32 @@ nsINode* nsContentUtils::Retarget(nsINode* aTargetA, nsINode* aTargetB) {
   return nullptr;
 }
 
+// static
+nsINode* nsContentUtils::GetAnElementForTiming(Element* aTarget,
+                                               const Document* aDocument,
+                                               nsIGlobalObject* aGlobal) {
+  if (!aTarget->IsInComposedDoc()) {
+    return nullptr;
+  }
+
+  if (!aDocument) {
+    nsCOMPtr<nsPIDOMWindowInner> inner = do_QueryInterface(aGlobal);
+    if (!inner) {
+      return nullptr;
+    }
+    aDocument = inner->GetExtantDoc();
+  }
+
+  MOZ_ASSERT(aDocument);
+
+  if (aTarget->GetUncomposedDocOrConnectedShadowRoot() != aDocument ||
+      !aDocument->IsCurrentActiveDocument()) {
+    return nullptr;
+  }
+
+  return aTarget;
+}
+
 // static
 nsresult nsContentUtils::GetInclusiveAncestors(nsINode* aNode,
                                                nsTArray<nsINode*>& aArray) {

dom/base/nsContentUtils.h

@@ -432,6 +432,13 @@ class nsContentUtils {
    */
   static nsINode* Retarget(nsINode* aTargetA, nsINode* aTargetB);
 
+  /**
+   * @see https://wicg.github.io/element-timing/#get-an-element
+   */
+  static nsINode* GetAnElementForTiming(Element* aTarget,
+                                        const Document* aDocument,
+                                        nsIGlobalObject* aGlobal);
+
   /*
    * https://dom.spec.whatwg.org/#concept-tree-inclusive-ancestor.
    *

dom/performance/PerformanceEventTiming.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/Performance.h"
 #include "mozilla/dom/Event.h"
+#include "nsContentUtils.h"
 #include "nsIDocShell.h"
 #include <algorithm>
 
@@ -167,16 +168,18 @@ void PerformanceEventTiming::BufferEntryIfNeeded() {
 }
 
 nsINode* PerformanceEventTiming::GetTarget() const {
-  if (!mTarget) {
+  nsCOMPtr<Element> element = do_QueryReferent(mTarget);
+  if (!element) {
     return nullptr;
   }
 
-  nsCOMPtr<nsINode> target = do_QueryReferent(mTarget);
-  if (!target || !target->IsInUncomposedDoc()) {
+  nsCOMPtr<nsPIDOMWindowInner> global =
+      do_QueryInterface(element->GetOwnerGlobal());
+  if (!global) {
     return nullptr;
   }
-
-  return target;
+  return nsContentUtils::GetAnElementForTiming(element, global->GetExtantDoc(),
+                                               mPerformance->GetParentObject());
 }
 
 void PerformanceEventTiming::FinalizeEventTiming(EventTarget* aTarget) {
@@ -191,36 +194,13 @@ void PerformanceEventTiming::FinalizeEventTiming(EventTarget* aTarget) {
 
   mProcessingEnd = mPerformance->NowUnclamped();
 
-  nsINode* node = nsINode::FromEventTarget(aTarget);
-  if (!node || node->ChromeOnlyAccess()) {
+  Element* element = Element::FromEventTarget(aTarget);
+  if (!element || element->ChromeOnlyAccess()) {
     return;
   }
 
-  mTarget = do_GetWeakReference(GetAnElement(node, global->GetExtantDoc()));
+  mTarget = do_GetWeakReference(element);
 
   mPerformance->InsertEventTimingEntry(this);
 }
-
-nsINode* PerformanceEventTiming::GetAnElement(nsINode* aTarget,
-                                              const Document* aDocument) {
-  if (!aTarget->IsInUncomposedDoc()) {
-    return nullptr;
-  }
-
-  if (!aDocument) {
-    nsCOMPtr<nsPIDOMWindowInner> inner =
-        do_QueryInterface(mPerformance->GetParentObject());
-    MOZ_ASSERT(inner);
-    aDocument = inner->GetExtantDoc();
-  }
-
-  MOZ_ASSERT(aDocument);
-
-  if (aTarget->GetComposedDoc() != aDocument ||
-      !aDocument->IsCurrentActiveDocument()) {
-    return nullptr;
-  }
-
-  return aTarget;
-}
 }  // namespace mozilla::dom

dom/performance/PerformanceEventTiming.h

@@ -114,9 +114,6 @@ class PerformanceEventTiming final
 
   ~PerformanceEventTiming() = default;
 
-  // Perform the get an element algorithm
-  nsINode* GetAnElement(nsINode* aTarget, const Document* aDocument);
-
   RefPtr<Performance> mPerformance;
 
   DOMHighResTimeStamp mProcessingStart;