setContentFrame() should be moved to the Frame constructor

https://bugs.webkit.org/show_bug.cgi?id=259697
rdar://113217067

Reviewed by Alex Christensen.

* Source/WebCore/page/Frame.cpp:
(WebCore::Frame::Frame):
* Source/WebCore/page/LocalFrame.cpp:
(WebCore::LocalFrame::LocalFrame):
* Source/WebKit/WebProcess/WebPage/WebFrame.cpp:
(WebKit::WebFrame::didCommitLoadInAnotherProcess):

Canonical link: https://commits.webkit.org/266491@main

Source/WebCore/page/Frame.cpp

@@ -49,6 +49,9 @@ Frame::Frame(Page& page, FrameIdentifier frameID, FrameType frameType, HTMLFrame
 {
     if (parent)
         parent->tree().appendChild(*this);
+
+    if (ownerElement)
+        ownerElement->setContentFrame(*this);
 }
 
 Frame::~Frame()

Source/WebCore/page/LocalFrame.cpp

@@ -159,11 +159,8 @@ LocalFrame::LocalFrame(Page& page, UniqueRef<LocalFrameLoaderClient>&& frameLoad
     ProcessWarming::initializeNames();
     StaticCSSValuePool::init();
 
-    if (ownerElement) {
-        if (auto* localMainFrame = dynamicDowncast<LocalFrame>(mainFrame()))
-            localMainFrame->selfOnlyRef();
-        ownerElement->setContentFrame(*this);
-    }
+    if (auto* localMainFrame = dynamicDowncast<LocalFrame>(mainFrame()); localMainFrame && ownerElement)
+        localMainFrame->selfOnlyRef();
 
 #ifndef NDEBUG
     frameCounter.increment();

Source/WebKit/WebProcess/WebPage/WebFrame.cpp

@@ -384,11 +384,8 @@ void WebFrame::didCommitLoadInAnotherProcess(std::optional<WebCore::LayerHosting
 
     m_coreFrame = newFrame.get();
 
-    // FIXME: This is also done in the WebCore::Frame constructor. Move one to make this more symmetric.
-    if (ownerElement) {
-        ownerElement->setContentFrame(*m_coreFrame);
+    if (ownerElement)
         ownerElement->scheduleInvalidateStyleAndLayerComposition();
-    }
 }
 
 void WebFrame::removeFromTree()