Group ConnectToApplication-related info into a params struct.

mojo/shell/identity.cc

Index: mojo/shell/identity.cc
diff --git a/mojo/shell/identity.cc b/mojo/shell/identity.cc
index 8bb4be973e946f3b8147e43249f6d48a42a50b7f..b3d045094ae16f63fa3c8b11a7726b8bad9a60b5 100644
--- a/mojo/shell/identity.cc
+++ b/mojo/shell/identity.cc
@@ -9,6 +9,8 @@
 namespace mojo {
 namespace shell {
 
+Identity::Identity() {}
+
 Identity::Identity(const GURL& in_url, const std::string& in_qualifier)
     : url(GetBaseURLAndQuery(in_url, nullptr)),
       qualifier(in_qualifier.empty() ? url.spec() : in_qualifier) {}