Switch SupportsUserData uses to use unique_ptr.

chrome/browser/extensions/api/tab_capture/offscreen_tab.h

 // Copyright 2015 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_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_
 #define CHROME_BROWSER_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 18 matching lines @@
 // is about to be destroyed, its associated OffscreenTabsOwner and all of its
 // OffscreenTab instances are destroyed.
 //
 // Usage:
 //
 //   OffscreenTabsOwner::Get(extension_contents)
 //       ->OpenNewTab(start_url, size, std::string());
 //
 // This class operates exclusively on the UI thread and so is not thread-safe.
 class OffscreenTabsOwner
-    : protected content::WebContentsUserData<OffscreenTabsOwner> {
+    : public content::WebContentsUserData<OffscreenTabsOwner> {
  public:
   ~OffscreenTabsOwner() final;
 
   // Returns the OffscreenTabsOwner instance associated with the given extension
   // background page's WebContents.  Never returns nullptr.
   static OffscreenTabsOwner* Get(content::WebContents* extension_web_contents);
 
   // Instantiate a new offscreen tab and navigate it to |start_url|.  The new
   // tab's main frame will start out with the given |initial_size| in DIP
   // coordinates.  If too many offscreen tabs are already running, nothing
@@ skipping 161 matching lines @@
   // This is false until after the Start() method is called, and capture of the
   // |offscreen_tab_web_contents_| is first detected.
   bool content_capture_was_detected_;
 
   DISALLOW_COPY_AND_ASSIGN(OffscreenTab);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_