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

chrome/browser/chrome_content_browser_client.h

Index: chrome/browser/chrome_content_browser_client.h
diff --git a/chrome/browser/chrome_content_browser_client.h b/chrome/browser/chrome_content_browser_client.h
index 40e700f311f5a8e0a4f411c57f4cde31cd8cd317..a456f7b3ca5da77459ac57c3ddc3f9c21fbfa1da 100644
--- a/chrome/browser/chrome_content_browser_client.h
+++ b/chrome/browser/chrome_content_browser_client.h
@@ -281,8 +281,10 @@ class ChromeContentBrowserClient : public content::ContentBrowserClient {
                                   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,
+               const base::Callback<void(content::WebContents*)>& callback)
+      override;
 
  private:
   friend class DisableWebRtcEncryptionFlagTest;