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

content/shell/browser/shell_content_browser_client.cc

Index: content/shell/browser/shell_content_browser_client.cc
diff --git a/content/shell/browser/shell_content_browser_client.cc b/content/shell/browser/shell_content_browser_client.cc
index fce64075ebc1a9ef72e88170f5e6670546198d67..9b8a2f458b86f6ab6db384a83f77d458644adae4 100644
--- a/content/shell/browser/shell_content_browser_client.cc
+++ b/content/shell/browser/shell_content_browser_client.cc
@@ -10,6 +10,7 @@
 #include "base/files/file_util.h"
 #include "base/path_service.h"
 #include "base/strings/utf_string_conversions.h"
+#include "content/public/browser/page_navigator.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/resource_dispatcher_host.h"
 #include "content/public/browser/storage_partition.h"
@@ -302,6 +303,14 @@ ShellContentBrowserClient::GetDevToolsManagerDelegate() {
   return new ShellDevToolsManagerDelegate(browser_context());
 }
 
+WebContents* ShellContentBrowserClient::OpenURL(BrowserContext* browser_context,
+                                                const OpenURLParams& params) {
+  return Shell::CreateNewWindow(browser_context,
+                                params.url,
+                                nullptr,
+                                gfx::Size())->web_contents();
+}
+
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
 void ShellContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
     const base::CommandLine& command_line,