Allow window.open to open in a new process when using TiledCoreAnimat…

…ionDrawingArea

https://bugs.webkit.org/show_bug.cgi?id=260059
rdar://111064288

Reviewed by J Pascoe.

When using TiledCoreAnimationDrawingArea and after a cross-site window.open, we have a WebPage
that has only RemoteFrames, which would use RemoteLayerTreeDrawingArea in most cases except
pre-Sonoma macOS and 2-core CPUs.  This WebPage only exists to hold RemoteFrames to proxy messages
back and forth, so it doesn't need to draw.  We just want it to not crash.

Add a null check and an early return in updateRendering like we do when layerTreeStateIsFrozen returns true.
Covered by the API test SiteIsolation.BasicPostMessageWindowOpen on pre-Sonoma macOS.

* Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml:
* Source/WebKit/UIProcess/mac/WebViewImpl.mm:
(WebKit::WebViewImpl::WebViewImpl):
* Source/WebKit/WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::hasRootFrames):
* Source/WebKit/WebProcess/WebPage/WebPage.h:
* Source/WebKit/WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm:
(WebKit::TiledCoreAnimationDrawingArea::updateRendering):

Canonical link: https://commits.webkit.org/266823@main

Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml

@@ -5201,9 +5201,12 @@ ProcessSwapOnCrossSiteWindowOpenEnabled:
    category: networking
    humanReadableName: "Swap Processes on Cross-Site Window Open"
    humanReadableDescription: "Swap WebContent Processes on cross-site window.open"
-   webcoreBinding: none
    exposed: [ WebKit ]
    defaultValue:
+     WebCore:
+       default: false
+     WebKitLegacy:
+       default: false
      WebKit:
        default: false
 

Source/WebKit/UIProcess/mac/WebViewImpl.mm

@@ -1173,10 +1173,6 @@ static bool isInRecoveryOS()
         if (m_page->preferences().siteIsolationEnabled())
             result = true;
 
-        // FIXME: Either make this work with TiledCoreAnimationDrawingArea or only enable it where remote layer trees are used.
-        if (m_page->preferences().processSwapOnCrossSiteWindowOpenEnabled())
-            result = true;
-
         if (isInRecoveryOS()) {
             // Temporarily disable UI side compositing in Recovery OS <rdar://107964149>.
             WTFLogAlways("Disabling UI side compositing in Recovery OS");

Source/WebKit/WebProcess/WebPage/WebPage.cpp

@@ -4802,6 +4802,16 @@ void WebPage::updateRendering()
 #endif
 }
 
+bool WebPage::hasRootFrames()
+{
+    bool result = m_page && !m_page->rootFrames().isEmptyIgnoringNullReferences();
+    if (!result) {
+        ASSERT(m_page->settings().processSwapOnCrossSiteWindowOpenEnabled());
+        ASSERT(!m_page->settings().siteIsolationEnabled());
+    }
+    return result;
+}
+
 void WebPage::didUpdateRendering()
 {
     didPaintLayers();

Source/WebKit/WebProcess/WebPage/WebPage.h

@@ -459,6 +459,7 @@ class WebPage : public API::ObjectImpl<API::Object::Type::BundlePage>, public IP
 
     void layoutIfNeeded();
     void updateRendering();
+    bool hasRootFrames();
     bool shouldTriggerRenderingUpdate(unsigned rescheduledRenderingUpdateCount) const;
     void finalizeRenderingUpdate(OptionSet<WebCore::FinalizeRenderingUpdateFlags>);
 

Source/WebKit/WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm

@@ -349,6 +349,9 @@
     if (layerTreeStateIsFrozen())
         return;
 
+    if (UNLIKELY(!m_webPage.hasRootFrames()))
+        return;
+
     @autoreleasepool {
         scaleViewToFitDocumentIfNeeded();
 
@@ -365,8 +368,10 @@
         }
 
         FloatRect visibleRect = [m_hostingLayer frame];
-        if (auto exposedRect = m_webPage.localMainFrameView()->viewExposedRect())
-            visibleRect.intersect(*exposedRect);
+        if (auto* localMainFrameView = m_webPage.localMainFrameView()) {
+            if (auto exposedRect = localMainFrameView->viewExposedRect())
+                visibleRect.intersect(*exposedRect);
+        }
 
         // Because our view-relative overlay root layer is not attached to the main GraphicsLayer tree, we need to flush it manually.
         if (m_viewOverlayRootLayer)