Fix build error in headless_web_contents_impl.cc

e2df1d70 adds a new parameter to
WebContentsDelegate::WebContentsCreated. This CL updates the
implementation in headless_web_contents_impl.cc accordingly.

BUG=649855
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2385123004
Cr-Commit-Position: refs/heads/master@{#422745}

headless/lib/browser/headless_web_contents_impl.cc

@@ -66,6 +66,7 @@ class HeadlessWebContentsImpl::Delegate : public content::WebContentsDelegate {
       : browser_context_(browser_context) {}
 
   void WebContentsCreated(content::WebContents* source_contents,
+                          int opener_render_process_id,
                           int opener_render_frame_id,
                           const std::string& frame_name,
                           const GURL& target_url,