Add a hack to set shouldPaint to true for force-composited iframes.

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index c794ef3ec79ee6eec003dd3095d2286786035e8d..20ff7bd117ec468123e2eea9598c58412aeb33d9 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -2441,15 +2441,25 @@ bool PaintLayer::childBackgroundIsKnownToBeOpaqueInRect(const LayoutRect& localR
     return false;
 }
 
-bool PaintLayer::shouldBeSelfPaintingLayer() const
+bool PaintLayer::isSelfPaintingLayerForIntrinsicOrScrollingReasons() const
 {
-    if (layoutObject()->isLayoutPart() && toLayoutPart(layoutObject())->requiresAcceleratedCompositing())
-        return true;
     return layoutObject()->layerTypeRequired() == NormalPaintLayer
         || (m_scrollableArea && m_scrollableArea->hasOverlayScrollbars())
         || needsCompositedScrolling();
 }
 
+bool PaintLayer::shouldBeSelfPaintingLayer() const
+{
+    if (layoutObject()->isLayoutPart() && toLayoutPart(layoutObject())->requiresAcceleratedCompositing())
+        return true;
+    return isSelfPaintingLayerForIntrinsicOrScrollingReasons();
+}
+
+bool PaintLayer::isSelfPaintingOnlyBecauseIsCompositedPart() const
+{
+    return shouldBeSelfPaintingLayer() && !isSelfPaintingLayerForIntrinsicOrScrollingReasons();
+}
+
 void PaintLayer::updateSelfPaintingLayer()
 {
     bool isSelfPaintingLayer = shouldBeSelfPaintingLayer();