Use InterstitialPage through a delegate interface instead of deriving from it.

content/public/browser/interstitial_page_delegate.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_BROWSER_INTERSTITIAL_PAGE_DELEGATE_H_
+#define CONTENT_PUBLIC_BROWSER_INTERSTITIAL_PAGE_DELEGATE_H_
+
+#include <string>
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+class NavigationEntry;
+struct RendererPreferences;
+
+// Controls and provides the html for an interstitial page. The delegate is
+// owned by the InterstitialPage.
+class InterstitialPageDelegate {
+ public:
+  virtual ~InterstitialPageDelegate() {}
+
+  // Return the HTML that should be displayed in the page.
+  virtual std::string GetHTMLContents() = 0;
+
+  // Called when the interstitial is proceeded or cancelled. Note that this may
+  // be called by content directly even if the embedder didn't call Proceed or
+  // DontProceed on InterstitialPage, since navigations etc may cancel them.
+  virtual void OnProceed() {}
+  virtual void OnDontProceed() {}
+
+  // Invoked when the page sent a command through DOMAutomation.

[Avi (use Gerrit), 2012/02/07 00:33:50]

I thought DOMAutomation was a chrome concept :)

[jam, 2012/02/07 01:10:05]

the larger automation code is. But this unfortunately named class is used for
interstitials and not just automation. it probably needs to be renamed

+  virtual void CommandReceived(const std::string& command) {}
+
+  // Invoked with the NavigationEntry that is going to be added to the
+  // navigation controller.
+  // Gives an opportunity to delegates to set states on the |entry|.
+  // Note that this is only called if the InterstitialPage was constructed with
+  // |new_navigation| set to true.
+  virtual void OverrideEntry(content::NavigationEntry* entry) {}
+
+  // Allows the delegate to override the renderer preferences structure that's
+  // sent to the new RenderViewHost.
+  virtual void OverrideRendererPrefs(content::RendererPreferences* prefs) {}
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_INTERSTITIAL_PAGE_DELEGATE_H_