Revise comments on various Shell interfaces. Make some methods private on ShellConnection.

ui/views/mus/platform_test_helper_mus.cc

Index: ui/views/mus/platform_test_helper_mus.cc
diff --git a/ui/views/mus/platform_test_helper_mus.cc b/ui/views/mus/platform_test_helper_mus.cc
index f34206e68ea165b60d065700879d45ad8f8d7189..68e2f28bce9b2bd969e861e2d95e1316b713468b 100644
--- a/ui/views/mus/platform_test_helper_mus.cc
+++ b/ui/views/mus/platform_test_helper_mus.cc
@@ -38,7 +38,8 @@ class PlatformTestHelperMus : public PlatformTestHelper {
     shell_connection_->WaitForInitialize();
     // ui/views/mus requires a WindowManager running, for now use the desktop
     // one.
-    shell_connection_->Connect("mojo:desktop_wm");
+    mojo::Shell* shell = shell_connection_.get();
+    shell->Connect("mojo:desktop_wm");
     WindowManagerConnection::Create(shell_connection_.get());
   }