Mojom: Blanket change to mark all pointer/handle fields as nullable.

mojo/public/interfaces/application/shell.mojom

Index: mojo/public/interfaces/application/shell.mojom
diff --git a/mojo/public/interfaces/application/shell.mojom b/mojo/public/interfaces/application/shell.mojom
index f2a39fc3f2bc64ffffb36506ebabd812fffba41f..a9ce05f49519b80dfbc3780d9bf13537c7ea21cd 100644
--- a/mojo/public/interfaces/application/shell.mojom
+++ b/mojo/public/interfaces/application/shell.mojom
@@ -12,7 +12,7 @@ module mojo {
 interface Shell {
   // Loads url. mojo:{service} will result in the user of the value of the
   // --origin flag to the shell being used.
-  ConnectToApplication(string application_url, ServiceProvider& provider);
+  ConnectToApplication(string? application_url, ServiceProvider&? provider);
 };
 
 }