[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 28bc092d96c980dc3ff5ca091fa766518c30d619..9f1e1f48d49290b51c3bc36e3dcfb085a2d52710 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -4135,6 +4135,20 @@ void WebViewImpl::removePageOverlay(WebPageOverlay* overlay)
         m_pageOverlays = nullptr;
 }
 
+void WebViewImpl::addPageOverlay(PageOverlay::Painter* overlayPainter, int zOrder)
+{
+    if (!m_pageOverlays)
+        m_pageOverlays = PageOverlayList::create(this);
+
+    m_pageOverlays->add(overlayPainter, zOrder);
+}
+
+void WebViewImpl::removePageOverlay(PageOverlay::Painter* overlayPainter)
+{
+    if (m_pageOverlays && m_pageOverlays->remove(overlayPainter) && m_pageOverlays->empty())
+        m_pageOverlays = nullptr;
+}
+
 void WebViewImpl::setOverlayLayer(GraphicsLayer* layer)
 {
     if (!m_rootGraphicsLayer)