Mojo C++ bindings: switch services/navigation mojom target to use STL types.

services/navigation/view_impl.cc

Index: services/navigation/view_impl.cc
diff --git a/services/navigation/view_impl.cc b/services/navigation/view_impl.cc
index 54d958206ce3bc52cba56301efae96a11bd2566c..bb6145d7549c0e39ce39f35d0a6211e29519f299 100644
--- a/services/navigation/view_impl.cc
+++ b/services/navigation/view_impl.cc
@@ -115,7 +115,7 @@ void ViewImpl::GetWindowTreeClient(ui::mojom::WindowTreeClientRequest request) {
       base::MakeUnique<ui::WindowTreeClient>(this, nullptr, std::move(request));
 }
 
-void ViewImpl::ShowInterstitial(const mojo::String& html) {
+void ViewImpl::ShowInterstitial(const std::string& html) {
   content::InterstitialPage* interstitial =
       content::InterstitialPage::Create(web_view_->GetWebContents(),
                                         false,