Move iframe and plugin compositing triggers into additionalCompositingReasons

Source/core/rendering/RenderPart.cpp

Index: Source/core/rendering/RenderPart.cpp
diff --git a/Source/core/rendering/RenderPart.cpp b/Source/core/rendering/RenderPart.cpp
index c535ae437e87597544e4e2aeb8cac49654cad4d9..27c851660dfaa09bd7ad89e19242cf911befbfcc 100644
--- a/Source/core/rendering/RenderPart.cpp
+++ b/Source/core/rendering/RenderPart.cpp
@@ -142,4 +142,11 @@ bool RenderPart::nodeAtPoint(const HitTestRequest& request, HitTestResult& resul
     return RenderWidget::nodeAtPoint(request, result, locationInContainer, accumulatedOffset, action);
 }
 
+CompositingReasons RenderPart::additionalCompositingReasons(CompositingTriggerFlags) const
+{
+    if (requiresAcceleratedCompositing())
+        return CompositingReasonIFrame;
+    return CompositingReasonNone;
+}
+
 }