Use ShellPtr type in ApplicationLoader instead of untyped handles

shell/android/ui_application_loader_android.h

Index: shell/android/ui_application_loader_android.h
diff --git a/shell/android/ui_application_loader_android.h b/shell/android/ui_application_loader_android.h
index 26ac13b52f79ff817be7e76c6a2bfdbbd9c5f9bc..a40a41a702949a4377757eda4f911a9a4fcba1a7 100644
--- a/shell/android/ui_application_loader_android.h
+++ b/shell/android/ui_application_loader_android.h
@@ -29,7 +29,7 @@ class UIApplicationLoader : public ApplicationLoader {
   // ApplicationLoader overrides:
   void Load(ApplicationManager* manager,
             const GURL& url,
-            ScopedMessagePipeHandle shell_handle,
+            ShellPtr shell,
             LoadCallback callback) override;
   void OnApplicationError(ApplicationManager* manager,
                           const GURL& url) override;
@@ -43,7 +43,7 @@ class UIApplicationLoader : public ApplicationLoader {
   // isn't thread safe).
   void LoadOnUIThread(ApplicationManager* manager,
                       const GURL& url,
-                      ScopedMessagePipeHandle shell_handle);
+                      ShellPtr shell);
   void OnApplicationErrorOnUIThread(ApplicationManager* manager,
                                     const GURL& url);
   void ShutdownOnUIThread();