Add a FOUC painting test.

Source/platform/graphics/GraphicsLayer.cpp

Index: Source/platform/graphics/GraphicsLayer.cpp
diff --git a/Source/platform/graphics/GraphicsLayer.cpp b/Source/platform/graphics/GraphicsLayer.cpp
index 6c27628d2cea91ee20f22808ca0b84abb2ca9c98..11c803a0b782ff2660afef2c6affac8d0595f001 100644
--- a/Source/platform/graphics/GraphicsLayer.cpp
+++ b/Source/platform/graphics/GraphicsLayer.cpp
@@ -64,6 +64,8 @@
 
 namespace blink {
 
+static bool s_drawDebugRedFill = true;
+
 // TODO(wangxianzhu): Remove this when we no longer invalidate rects.
 struct PaintInvalidationTrackingInfo {
     Vector<FloatRect> invalidationRects;
@@ -149,6 +151,11 @@ GraphicsLayer::~GraphicsLayer()
     ASSERT(!m_parent);
 }
 
+void GraphicsLayer::setDrawDebugRedFillForTesting(bool enabled)
+{
+    s_drawDebugRedFill = enabled;
+}
+
 void GraphicsLayer::setParent(GraphicsLayer* layer)
 {
     ASSERT(!layer || !layer->hasAncestor(this));
@@ -290,7 +297,7 @@ void GraphicsLayer::paintGraphicsLayerContents(GraphicsContext& context, const I
         m_debugInfo.clearAnnotatedInvalidateRects();
     incrementPaintCount();
 #ifndef NDEBUG
-    if (m_displayItemList && contentsOpaque()) {
+    if (m_displayItemList && contentsOpaque() && s_drawDebugRedFill) {
         ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
         FloatRect rect(FloatPoint(), size());
         if (!DrawingRecorder::useCachedDrawingIfPossible(context, *this, DisplayItem::DebugRedFill)) {
@@ -460,6 +467,14 @@ void GraphicsLayer::resetTrackedPaintInvalidations()
     paintInvalidationTrackingMap().remove(this);
 }
 
+bool GraphicsLayer::hasTrackedPaintInvalidations() const
+{
+    PaintInvalidationTrackingMap::iterator it = paintInvalidationTrackingMap().find(this);
+    if (it != paintInvalidationTrackingMap().end())
+        return !it->value.invalidationRects.isEmpty();
+    return false;
+}
+
 void GraphicsLayer::trackPaintInvalidationRect(const FloatRect& rect)
 {
     if (rect.isEmpty())