Emit an error log line when attempting to connect to an app at an invalid URL.

mojo/application_manager/application_manager.cc

Index: mojo/application_manager/application_manager.cc
diff --git a/mojo/application_manager/application_manager.cc b/mojo/application_manager/application_manager.cc
index e99c627cf74cfeca6e60b1230856e23d25152136..443c3f1986f1fcdc22ac12e1615b5043936155cf 100644
--- a/mojo/application_manager/application_manager.cc
+++ b/mojo/application_manager/application_manager.cc
@@ -146,8 +146,12 @@ class ApplicationManager::ShellImpl : public Shell, public ErrorHandler {
       InterfaceRequest<ServiceProvider> in_service_provider) override {
     ServiceProviderPtr out_service_provider;
     out_service_provider.Bind(in_service_provider.PassMessagePipe());
-    manager_->ConnectToApplication(
-        app_url.To<GURL>(), url_, out_service_provider.Pass());
+    GURL app_gurl(app_url);
+    if (!app_gurl.is_valid()) {
+      LOG(ERROR) << "Error: invalid URL: " << app_url;
+      return;
+    }
+    manager_->ConnectToApplication(app_gurl, url_, out_service_provider.Pass());
   }
 
   // ErrorHandler implementation:
@@ -229,6 +233,7 @@ void ApplicationManager::ConnectToApplication(
     const GURL& requested_url,
     const GURL& requestor_url,
     ServiceProviderPtr service_provider) {
+  DCHECK(requested_url.is_valid());
   ApplicationLoader* loader = GetLoaderForURL(requested_url,
                                               DONT_INCLUDE_DEFAULT_LOADER);
   if (loader) {