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

content/public/browser/content_browser_client.cc

Index: content/public/browser/content_browser_client.cc
diff --git a/content/public/browser/content_browser_client.cc b/content/public/browser/content_browser_client.cc
index acacd9850ca0507b98dbace2a9d72bc5eea76747..f9177ed786bbadf9190431d6c8e4bacb13ce2ff0 100644
--- a/content/public/browser/content_browser_client.cc
+++ b/content/public/browser/content_browser_client.cc
@@ -342,9 +342,11 @@ ContentBrowserClient::GetPresentationServiceDelegate(
   return nullptr;
 }
 
-WebContents* ContentBrowserClient::OpenURL(BrowserContext* browser_context,
-                                           const OpenURLParams& params) {
-  return nullptr;
+void ContentBrowserClient::OpenURL(
+    content::BrowserContext* browser_context,
+    const content::OpenURLParams& params,
+    const base::Callback<void(content::WebContents*)>& callback) {
+  callback.Run(nullptr);
 }
 
 #if defined(OS_WIN)