api-impl: misc stubs and fixes for Spotify

src/api-impl/android/app/Activity.java

@@ -97,6 +97,7 @@ public class Activity extends ContextThemeWrapper implements Window.Callback {
 				break;
 			}
 		}
+
 		app_label = r.getText(pkg.applicationInfo.labelRes);
 		if (label != null) {
 			setTitle(label);
@@ -568,4 +569,6 @@ public class Activity extends ContextThemeWrapper implements Window.Callback {
 	public static native void nativeOpenURI(String uri);
 	public native void nativeFileChooser(int action, String type, String title, int requestCode);
 	public void reportFullyDrawn() {}
+	public void setVisible(boolean visible) {}
+	public Uri getReferrer() { return null; }
 }

src/api-impl/android/app/ActivityManager.java

@@ -2,7 +2,11 @@ package android.app;
 
 import android.content.pm.ConfigurationInfo;
 import android.graphics.Bitmap;
+import android.os.IBinder;
+import android.os.Parcel;
+import android.os.Parcelable;
 
+import java.util.ArrayList;
 import java.util.List;
 
 public class ActivityManager {
@@ -46,4 +50,32 @@ public class ActivityManager {
 	public static void getMyMemoryState(RunningAppProcessInfo outInfo) {}
 
 	public boolean clearApplicationUserData() {return false;}
+
+	public static class AppTask {}
+	public List<ActivityManager.AppTask> getAppTasks() {
+		return new ArrayList<>();
+	}
+	
+	public static class RunningServiceInfo implements Parcelable {
+		public RunningServiceInfo() {
+		}
+
+		public int describeContents() {
+			return 0;
+		}
+
+		public void writeToParcel(Parcel dest, int flags) {
+			return;
+		}
+
+		public void readFromParcel(Parcel source) {
+			return;
+		}
+	}     
+
+
+	public List<RunningServiceInfo> getRunningServices(int maxNum)
+		throws SecurityException {
+			return new ArrayList<>();
+	}
 }