[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/web/WebDevToolsAgentImpl.h

Index: Source/web/WebDevToolsAgentImpl.h
diff --git a/Source/web/WebDevToolsAgentImpl.h b/Source/web/WebDevToolsAgentImpl.h
index 422a282104c4649f10f1d3f729125d0456ecd120..9c386981ba033ec0b83a0d298019e40a8a4836d7 100644
--- a/Source/web/WebDevToolsAgentImpl.h
+++ b/Source/web/WebDevToolsAgentImpl.h
@@ -37,13 +37,14 @@
 #include "public/platform/WebSize.h"
 #include "public/platform/WebThread.h"
 #include "public/web/WebDevToolsAgent.h"
-#include "public/web/WebPageOverlay.h"
+#include "web/PageOverlay.h"
 #include "wtf/Forward.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
+class GraphicsContext;
 class LocalFrame;
 class InspectorClient;
 class InspectorController;
@@ -59,7 +60,7 @@ class WebDevToolsAgentImpl final
     : public WebDevToolsAgent
     , public InspectorClient
     , public InspectorFrontendChannel
-    , public WebPageOverlay
+    , public PageOverlay::Painter
     , private WebThread::TaskObserver {
 public:
     WebDevToolsAgentImpl(WebViewImpl* webViewImpl, WebDevToolsAgentClient* client);
@@ -105,8 +106,8 @@ public:
     virtual void dispatchKeyEvent(const PlatformKeyboardEvent&) override;
     virtual void dispatchMouseEvent(const PlatformMouseEvent&) override;
 
-    // WebPageOverlay
-    virtual void paintPageOverlay(WebCanvas*) override;
+    // PageOverlay::Painter implementation.
+    virtual void paintPageOverlay(GraphicsContext&) override;
 
     void flushPendingProtocolNotifications();