Introduce the abstract class WebViewBase, to decouple WebViewImpl.

third_party/WebKit/Source/web/ContextMenuClientImpl.h

Index: third_party/WebKit/Source/web/ContextMenuClientImpl.h
diff --git a/third_party/WebKit/Source/web/ContextMenuClientImpl.h b/third_party/WebKit/Source/web/ContextMenuClientImpl.h
index f69612fd7ab112ad43d58e78d7374a5e8b8c9b79..c54d53209fe9a44f455061fb9570e8020df9344d 100644
--- a/third_party/WebKit/Source/web/ContextMenuClientImpl.h
+++ b/third_party/WebKit/Source/web/ContextMenuClientImpl.h
@@ -37,12 +37,12 @@ namespace blink {
 
 class Document;
 class Editor;
-class WebViewImpl;
+class WebViewBase;
 struct WebContextMenuData;
 
 class ContextMenuClientImpl final : public ContextMenuClient {
  public:
-  explicit ContextMenuClientImpl(WebViewImpl* web_view) : web_view_(web_view) {}
+  explicit ContextMenuClientImpl(WebViewBase* web_view) : web_view_(web_view) {}
   ~ContextMenuClientImpl() override {}
   bool ShowContextMenu(const ContextMenu*, bool from_touch) override;
   void ClearContextMenu() override;
@@ -51,7 +51,7 @@ class ContextMenuClientImpl final : public ContextMenuClient {
   void PopulateCustomMenuItems(const ContextMenu*, WebContextMenuData*);
   static int ComputeEditFlags(Document&, Editor&);
   bool ShouldShowContextMenuFromTouch(const blink::WebContextMenuData&);
-  WebViewImpl* web_view_;
+  WebViewBase* web_view_;
 };
 
 }  // namespace blink