Refactor GuestView.

chrome/browser/guestview/guestview.h

Index: chrome/browser/guestview/guestview.h
diff --git a/chrome/browser/guestview/guestview.h b/chrome/browser/guestview/guestview.h
index 63b28bbda232fa1386c276da2cd080ed87a4121d..7d8c6ab8c191574431a3df71f685cc746a46f7af 100644
--- a/chrome/browser/guestview/guestview.h
+++ b/chrome/browser/guestview/guestview.h
@@ -82,11 +82,14 @@ class GuestView : public content::BrowserPluginGuestDelegate {
 
   virtual Type GetViewType() const;
 
-  // Returns a WebViewGuest if this GuestView belongs to a <webview>.
-  virtual WebViewGuest* AsWebView() = 0;
-
-  // Returns an AdViewGuest if the GuestView belongs to an <adview>.
-  virtual AdViewGuest* AsAdView() = 0;
+  // Returns a *ViewGuest if this GuestView is of the given view type.
+  template <class T>

[Xi Han, 2014/04/15 21:35:37]

We do not want a bunch of As*View functions, e.g.,AsAdView(), AsWebView() ect.
After introducing this template functions, we can obtain an *GuestView pointer
by using guest->As<*ViewGuest>() if this guest view is of the same type as the
given guest view.

+  T* As() {
+    if (GetViewType() == T::Type()) {
+      return static_cast<T*>(this);
+    }
+    return NULL;
+  }
 
   // Returns whether this guest has an associated embedder.
   bool attached() const { return !!embedder_web_contents_; }