Create an interface to access the two pane state

Create an new interface in the embedding provider,
this interface tells if settings app is in two pane or not.

To access the activity in the content provider, we need to store
the activity reference in the app application layer.

Test: See if two pane state is correct.
Bug: 203763572
Change-Id: Iae2245b84af2683d932f1900df9959dad98370d7

src/com/android/settings/SettingsApplication.java

@@ -16,13 +16,18 @@
 
 package com.android.settings;
 
+import android.app.Activity;
 import android.app.Application;
 
 import com.android.settings.activityembedding.ActivityEmbeddingRulesController;
 
+import java.lang.ref.WeakReference;
+
 /** Settings application which sets up activity embedding rules for the large screen device. */
 public class SettingsApplication extends Application {
 
+    private WeakReference<Activity> mHomeActivity = new WeakReference<>(null);
+
     @Override
     public void onCreate() {
         super.onCreate();
@@ -31,4 +36,12 @@ public class SettingsApplication extends Application {
                 new ActivityEmbeddingRulesController(this);
         controller.initRules();
     }
+
+    public void setHomeActivity(Activity homeActivity) {
+        mHomeActivity = new WeakReference<>(homeActivity);
+    }
+
+    public Activity getHomeActivity() {
+        return mHomeActivity.get();
+    }
 }