Attach a WebLayer to a frame element for out-of-process iframes.

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 33db879892691d68b3f0ce64515ea8630b8b1be1..1e99b8bc6a13ba0a3848caec9e72cf836c91d924 100644
--- a/Source/core/rendering/RenderPart.cpp
+++ b/Source/core/rendering/RenderPart.cpp
@@ -25,8 +25,9 @@
 #include "config.h"
 #include "core/rendering/RenderPart.h"
 
-#include "core/html/HTMLFrameElementBase.h"
+#include "core/frame/Frame.h"
 #include "core/frame/FrameView.h"
+#include "core/html/HTMLFrameElementBase.h"
 #include "core/plugins/PluginView.h"
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/RenderLayer.h"
@@ -85,6 +86,9 @@ bool RenderPart::requiresAcceleratedCompositing() const
         return false;
 
     HTMLFrameOwnerElement* element = toHTMLFrameOwnerElement(node());
+    if (element->contentFrame() && element->contentFrame()->platformLayer())
+        return true;
+
     if (Document* contentDocument = element->contentDocument()) {
         if (RenderView* view = contentDocument->renderView())
             return view->usesCompositing();