Use ShellPtr type in ApplicationLoader instead of untyped handles

shell/android/native_viewport_application_loader.cc

Index: shell/android/native_viewport_application_loader.cc
diff --git a/shell/android/native_viewport_application_loader.cc b/shell/android/native_viewport_application_loader.cc
index 9f96417d48cf9568ef2a0f80c4a7dfc8bf02c5c9..72996a7bd99797062d603717e2ad44aff2811ebd 100644
--- a/shell/android/native_viewport_application_loader.cc
+++ b/shell/android/native_viewport_application_loader.cc
@@ -19,10 +19,10 @@ NativeViewportApplicationLoader::~NativeViewportApplicationLoader() {
 
 void NativeViewportApplicationLoader::Load(ApplicationManager* manager,
                                            const GURL& url,
-                                           ScopedMessagePipeHandle shell_handle,
+                                           ShellPtr shell,
                                            LoadCallback callback) {
-  DCHECK(shell_handle.is_valid());
-  app_.reset(new ApplicationImpl(this, shell_handle.Pass()));
+  DCHECK(shell);
+  app_.reset(new ApplicationImpl(this, shell.Pass()));
 }
 
 void NativeViewportApplicationLoader::OnApplicationError(