Add PagedList.getLoadedCount

Test: ./gradlew paging:paging-common:test

Change-Id: Ic1be6e8630ff40185835e0611c0181e3db3fe2c9

diff --git a/paging/common/api/current.txt b/paging/common/api/current.txt
index 249d3f7..7bfadcb 100644
--- a/paging/common/api/current.txt
+++ b/paging/common/api/current.txt

@@ -92,6 +92,7 @@
     method public androidx.paging.PagedList.Config getConfig();
     method public abstract androidx.paging.DataSource<?, T> getDataSource();
     method public abstract java.lang.Object getLastKey();
+    method public int getLoadedCount();
     method public int getPositionOffset();
     method public boolean isDetached();
     method public boolean isImmutable();