Compute minimum repaint and show them in overlay

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index 22a86c8c894068b032899a3bafb6a5b8bc8f0c4f..baad07a49abcb63fa3a9c7a5cbbd46e28d3908ee 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -2029,6 +2029,17 @@ void Internals::updateLayoutIgnorePendingStylesheetsAndRunPostLayoutTasks(Node*
     document->updateLayoutIgnorePendingStylesheets(Document::RunPostLayoutTasksSynchronously);
 }
 
+void Internals::forceFullRepaint(Document* document, ExceptionState& exceptionState)
+{
+    if (!document || !document->view()) {
+        exceptionState.throwDOMException(InvalidAccessError, document ? "The document's view cannot be retrieved." : "The document provided is invalid.");
+        return;
+    }
+
+    if (RenderView *renderView = document->renderView())
+        renderView->repaintViewAndCompositedLayers();
+}
+
 PassRefPtrWillBeRawPtr<ClientRectList> Internals::draggableRegions(Document* document, ExceptionState& exceptionState)
 {
     return annotatedRegions(document, true, exceptionState);