Get rid of frame_->GetDocument() == this check in Document::Loader

Change-Id: I511771cfc43fca4d12b2f8e9b1239708d8fc8a76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2211939
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773289}

third_party/blink/renderer/core/dom/document.cc

@@ -7602,15 +7602,7 @@ void Document::CancelIdleCallback(int id) {
 }
 
 DocumentLoader* Document::Loader() const {
-  if (!GetFrame())
-    return nullptr;
-
-  // TODO(dcheng): remove this check. GetFrame() is guaranteed to be non-null
-  // only if GetFrame()->GetDocument() == this.
-  if (GetFrame()->GetDocument() != this)
-    return nullptr;
-
-  return GetFrame()->Loader().GetDocumentLoader();
+  return GetFrame() ? GetFrame()->Loader().GetDocumentLoader() : nullptr;
 }
 
 Node* EventTargetNodeForDocument(Document* doc) {

third_party/blink/renderer/core/timing/window_performance.cc

@@ -141,21 +141,13 @@ AtomicString SameOriginAttribution(Frame* observer_frame,
 }  // namespace
 
 static base::TimeTicks ToTimeOrigin(LocalDOMWindow* window) {
-  Document* document = window->document();
-  if (!document)
-    return base::TimeTicks();
-
-  DocumentLoader* loader = document->Loader();
-  if (!loader)
-    return base::TimeTicks();
-
+  DocumentLoader* loader = window->GetFrame()->Loader().GetDocumentLoader();
   return loader->GetTiming().ReferenceMonotonicTime();
 }
 
 WindowPerformance::WindowPerformance(LocalDOMWindow* window)
-    : Performance(
-          ToTimeOrigin(window),
-          window->document()->GetTaskRunner(TaskType::kPerformanceTimeline)),
+    : Performance(ToTimeOrigin(window),
+                  window->GetTaskRunner(TaskType::kPerformanceTimeline)),
       ExecutionContextClient(window) {
   DCHECK(GetFrame());
   DCHECK(GetFrame()->GetPerformanceMonitor());