Fix browser tests on Mac

headless/lib/browser/headless_web_contents_impl.cc

Index: headless/lib/browser/headless_web_contents_impl.cc
diff --git a/headless/lib/browser/headless_web_contents_impl.cc b/headless/lib/browser/headless_web_contents_impl.cc
index 42db63f54b4a54db9ff9f3a30e7866ca076fc92d..f75a2dea7c877e36582aed9241c1eed9e3dca4b3 100644
--- a/headless/lib/browser/headless_web_contents_impl.cc
+++ b/headless/lib/browser/headless_web_contents_impl.cc
@@ -204,6 +204,7 @@ bool HeadlessWebContentsImpl::OpenURL(const GURL& url) {
   params.transition_type = ui::PageTransitionFromInt(
       ui::PAGE_TRANSITION_TYPED | ui::PAGE_TRANSITION_FROM_ADDRESS_BAR);
   web_contents_->GetController().LoadURLWithParams(params);
+  web_contents_delegate_->ActivateContents(web_contents_.get());
   web_contents_->Focus();
   return true;
 }