Bug 1551716 - Simplify the cross-origin check in IntersectionObserver. r=mstange

Should've no behavior change given the spec issue, but it should read nicer.

Differential Revision: https://phabricator.services.mozilla.com/D31148

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

dom/base/DOMIntersectionObserver.cpp

@@ -190,25 +190,6 @@ void DOMIntersectionObserver::TakeRecords(
   mQueuedEntries.Clear();
 }
 
-static bool CheckSimilarOrigin(nsINode* aNode1, nsINode* aNode2) {
-  nsIPrincipal* principal1 = aNode1->NodePrincipal();
-  nsIPrincipal* principal2 = aNode2->NodePrincipal();
-  nsAutoCString baseDomain1;
-  nsAutoCString baseDomain2;
-
-  nsresult rv = principal1->GetBaseDomain(baseDomain1);
-  if (NS_FAILED(rv)) {
-    return principal1 == principal2;
-  }
-
-  rv = principal2->GetBaseDomain(baseDomain2);
-  if (NS_FAILED(rv)) {
-    return principal1 == principal2;
-  }
-
-  return baseDomain1 == baseDomain2;
-}
-
 static Maybe<nsRect> EdgeInclusiveIntersection(const nsRect& aRect,
                                                const nsRect& aOtherRect) {
   nscoord left = std::max(aRect.x, aOtherRect.x);
@@ -221,11 +202,33 @@ static Maybe<nsRect> EdgeInclusiveIntersection(const nsRect& aRect,
   return Some(nsRect(left, top, right - left, bottom - top));
 }
 
-enum class BrowsingContextInfo {
-  SimilarOriginBrowsingContext,
-  DifferentOriginBrowsingContext,
-  UnknownBrowsingContext
-};
+enum class BrowsingContextOrigin { Similar, Different, Unknown };
+
+// FIXME(emilio): The whole concept of "units of related similar-origin browsing
+// contexts" is gone, but this is still in the spec, see
+// https://github.com/w3c/IntersectionObserver/issues/161
+static BrowsingContextOrigin SimilarOrigin(const Element& aTarget,
+                                           const Element* aRoot) {
+  if (!aRoot) {
+    return BrowsingContextOrigin::Unknown;
+  }
+  nsIPrincipal* principal1 = aTarget.NodePrincipal();
+  nsIPrincipal* principal2 = aRoot->NodePrincipal();
+
+  if (principal1 == principal2) {
+    return BrowsingContextOrigin::Similar;
+  }
+
+  nsAutoCString baseDomain1;
+  nsAutoCString baseDomain2;
+  if (NS_FAILED(principal1->GetBaseDomain(baseDomain1)) ||
+      NS_FAILED(principal2->GetBaseDomain(baseDomain2))) {
+    return BrowsingContextOrigin::Different;
+  }
+
+  return baseDomain1 == baseDomain2 ? BrowsingContextOrigin::Similar
+                                    : BrowsingContextOrigin::Different;
+}
 
 void DOMIntersectionObserver::Update(Document* aDocument,
                                      DOMHighResTimeStamp time) {
@@ -347,22 +350,13 @@ void DOMIntersectionObserver::Update(Document* aDocument,
     }
 
     nsRect rootIntersectionRect;
-    BrowsingContextInfo isInSimilarOriginBrowsingContext =
-        BrowsingContextInfo::UnknownBrowsingContext;
-
     if (rootFrame && targetFrame) {
+      // FIXME(emilio): Why only if there are frames?
       rootIntersectionRect = rootRect;
     }
 
-    if (root && target) {
-      isInSimilarOriginBrowsingContext =
-          CheckSimilarOrigin(root, target)
-              ? BrowsingContextInfo::SimilarOriginBrowsingContext
-              : BrowsingContextInfo::DifferentOriginBrowsingContext;
-    }
-
-    if (isInSimilarOriginBrowsingContext ==
-        BrowsingContextInfo::SimilarOriginBrowsingContext) {
+    BrowsingContextOrigin origin = SimilarOrigin(*target, root);
+    if (origin == BrowsingContextOrigin::Similar) {
       rootIntersectionRect.Inflate(rootMargin);
     }
 
@@ -416,13 +410,12 @@ void DOMIntersectionObserver::Update(Document* aDocument,
     }
 
     if (target->UpdateIntersectionObservation(this, threshold)) {
-      QueueIntersectionObserverEntry(
-          target, time,
-          isInSimilarOriginBrowsingContext ==
-                  BrowsingContextInfo::DifferentOriginBrowsingContext
-              ? Nothing()
-              : Some(rootIntersectionRect),
-          targetRect, intersectionRect, intersectionRatio);
+      QueueIntersectionObserverEntry(target, time,
+                                     origin == BrowsingContextOrigin::Different
+                                         ? Nothing()
+                                         : Some(rootIntersectionRect),
+                                     targetRect, intersectionRect,
+                                     intersectionRatio);
     }
   }
 }