First step in enabling creating tabs without an Activity on Android.

chrome/browser/chrome_content_browser_client.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_CHROME_CONTENT_BROWSER_CLIENT_H_
 #define CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 263 matching lines @@
 #endif
 #if defined(OS_WIN)
   virtual const wchar_t* GetResourceDllName() override;
   virtual void PreSpawnRenderer(sandbox::TargetPolicy* policy,
                                 bool* success) override;
 #endif
   bool CheckMediaAccessPermission(content::BrowserContext* browser_context,
                                   const GURL& security_origin,
                                   content::MediaStreamType type) override;
 
-  content::WebContents* OpenURL(content::BrowserContext* browser_context,
-                                const content::OpenURLParams& params) override;
+  void OpenURL(content::BrowserContext* browser_context,
+               const content::OpenURLParams& params,
+               base::Callback<void(content::WebContents*)> callback) override;
 
  private:
   friend class DisableWebRtcEncryptionFlagTest;
 
 #if defined(ENABLE_WEBRTC)
   // Copies disable WebRTC encryption switch depending on the channel.
   static void MaybeCopyDisableWebRtcEncryptionSwitch(
       base::CommandLine* to_command_line,
       const base::CommandLine& from_command_line,
       VersionInfo::Channel channel);
@@ skipping 43 matching lines @@
   std::vector<ChromeContentBrowserClientParts*> extra_parts_;
 
   base::WeakPtrFactory<ChromeContentBrowserClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeContentBrowserClient);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_CHROME_CONTENT_BROWSER_CLIENT_H_