[DevTools] Make WebDevToolsAgentImpl own InspectorOverlayImpl.

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 5cad81413ed3bc132c289bf1d84e5a8f300fa7a8..7eda6903c03fe24fdc25bcc2f7cf0048409315bc 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -72,7 +72,6 @@ class DataObject;
 class DevToolsEmulator;
 class Frame;
 class FullscreenController;
-class InspectorOverlay;
 class InspectorOverlayImpl;
 class LinkHighlightImpl;
 class PageOverlay;
@@ -332,8 +331,6 @@ public:
 
     WebDevToolsAgentImpl* mainFrameDevToolsAgentImpl();
 
-    InspectorOverlay* inspectorOverlay();
-
     DevToolsEmulator* devToolsEmulator() const
     {
         return m_devToolsEmulator.get();
@@ -537,6 +534,8 @@ public:
     WebPageImportanceSignals& pageImportanceSignals() { return m_pageImportanceSignals; }
 
 private:
+    InspectorOverlayImpl* inspectorOverlay();
+
     void setPageScaleFactorAndLocation(float, const FloatPoint&);
 
     void scrollAndRescaleViewports(float scaleFactor, const IntPoint& mainFrameOrigin, const FloatPoint& visualViewportOrigin);