Revert of Unify desktop and Android tab helper instantiation.

chrome/browser/ui/browser_tab_contents.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 CHROME_BROWSER_UI_BROWSER_TAB_CONTENTS_H_
+#define CHROME_BROWSER_UI_BROWSER_TAB_CONTENTS_H_
+
+class Browser;
+
+namespace content {
+class WebContents;
+}
+
+namespace chrome {
+class BrowserTabStripModelDelegate;
+}
+
+namespace prerender {
+class PrerenderContents;
+}
+
+// A "tab contents" is a WebContents that is used as a tab in a browser
+// window, and thus is owned by a Browser's TabStripModel. The
+// BrowserTabContents class allows specific classes to attach the set of tab
+// helpers that is used for tab contents.
+//
+// TODO(avi): This list is rather large, and for most callers it's due to the
+// fact that they need tab helpers attached early to deal with arbitrary
+// content loaded into a WebContents that will later be added to the tabstrip.
+// Is there a better way to handle this? (Ideally, this list would contain
+// only Browser and BrowserTabStripModelDelegate.)
+class BrowserTabContents {
+ private:
+  // Browser and its TabStripModelDelegate have intimate control of tabs.
+  // TabAndroid is the equivalent on Android.
+  friend class Browser;
+  friend class chrome::BrowserTabStripModelDelegate;
+  friend class TabAndroid;
+
+  // chrome::Navigate creates WebContents that are destined for the tab strip,
+  // and that might have WebUI that immediately calls back into random tab
+  // helpers.
+  friend class BrowserNavigatorWebContentsAdoption;
+
+  // Prerendering loads pages that have arbitrary external content; it needs
+  // the full set of tab helpers to deal with it.
+  friend class prerender::PrerenderContents;
+
+  // Adopts the specified WebContents as a full-fledged browser tab, attaching
+  // all the associated tab helpers that are needed for the WebContents to
+  // serve in that role. It is safe to call this on a WebContents that was
+  // already adopted.
+  static void AttachTabHelpers(content::WebContents* web_contents);
+};
+
+#endif  // CHROME_BROWSER_UI_BROWSER_TAB_CONTENTS_H_