Plumb CompositedDisplayList to WebViewImpl

public/web/WebView.h

Index: public/web/WebView.h
diff --git a/public/web/WebView.h b/public/web/WebView.h
index b4c51fe6eda0df1b81fa14f911169b41c8f43f63..2b6065d0f4ae1ffe2449f8669850fbc22a94fd7d 100644
--- a/public/web/WebView.h
+++ b/public/web/WebView.h
@@ -46,6 +46,7 @@ namespace blink {
 
 class WebAXObject;
 class WebAutofillClient;
+class WebCompositedDisplayList;
 class WebCredentialManagerClient;
 class WebDragData;
 class WebFrame;
@@ -452,6 +453,10 @@ public:
     virtual void setVisibilityState(WebPageVisibilityState visibilityState,
                                     bool isInitialState) { }
 
+    // Graphics -------------------------------------------------------------
+
+    virtual WebCompositedDisplayList* compositedDisplayList() { return nullptr; }
+
     // PageOverlay ----------------------------------------------------------
 
     // Overlay this WebView with a solid color.