Use compositor for page popups.

Source/web/WebPagePopupImpl.h

Index: Source/web/WebPagePopupImpl.h
diff --git a/Source/web/WebPagePopupImpl.h b/Source/web/WebPagePopupImpl.h
index 66485f50478df25e5f02c75aecbf0a64562e9e2b..5b35c3901d4f8913c88b740475a09ec58a672067 100644
--- a/Source/web/WebPagePopupImpl.h
+++ b/Source/web/WebPagePopupImpl.h
@@ -38,6 +38,7 @@
 #include "wtf/RefCounted.h"
 
 namespace WebCore {
+class GraphicsLayer;
 class Page;
 class PagePopupClient;
 class PlatformKeyboardEvent;
@@ -46,6 +47,8 @@ class PlatformKeyboardEvent;
 namespace blink {
 
 class PagePopupChromeClient;
+class WebLayerTreeView;
+class WebLayer;
 class WebViewImpl;
 
 class WebPagePopupImpl FINAL :
@@ -69,6 +72,9 @@ private:
     virtual WebSize size() OVERRIDE;
     virtual void animate(double) OVERRIDE;
     virtual void layout() OVERRIDE;
+    virtual void enterForceCompositingMode(bool enter) OVERRIDE;
+    virtual void didExitCompositingMode() OVERRIDE;
+    virtual void willCloseLayerTreeView() OVERRIDE;
     virtual void paint(WebCanvas*, const WebRect&, PaintOptions = ReadbackFromCompositorIfAvailable) OVERRIDE;
     virtual void resize(const WebSize&) OVERRIDE;
     virtual void close() OVERRIDE;
@@ -84,6 +90,8 @@ private:
     explicit WebPagePopupImpl(WebWidgetClient*);
     bool initializePage();
     void destroyPage();
+    void setRootGraphicsLayer(WebCore::GraphicsLayer*);
+    void setIsAcceleratedCompositingActive(bool enter);
 
     WebWidgetClient* m_widgetClient;
     WebRect m_windowRectInScreen;
@@ -93,6 +101,11 @@ private:
     WebCore::PagePopupClient* m_popupClient;
     bool m_closing;
 
+    WebLayerTreeView* m_layerTreeView;
+    WebLayer* m_rootLayer;
+    WebCore::GraphicsLayer* m_rootGraphicsLayer;
+    bool m_isAcceleratedCompositingActive;
+
     friend class WebPagePopup;
     friend class PagePopupChromeClient;
 };