Add ContentBrowserClient::OpenURL to allow tab opening wo/ WebContents.

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 884ae0d3176e7cba4486f66aae173f5ee7b88a5e..9db212146c6d6a3779883fbb603699b75aa18dbe 100644
--- a/chrome/browser/chrome_content_browser_client.h
+++ b/chrome/browser/chrome_content_browser_client.h
@@ -273,6 +273,9 @@ 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;
+
  private:
   friend class DisableWebRtcEncryptionFlagTest;