Bug 1269914 - Add probe for reaching end of History list. r=margaret

MozReview-Commit-ID: E7eXsF8Voc9

--HG--
extra : rebase_source : aee5c00b342a5caa3125216f66f2925612d792b2

mobile/android/base/java/org/mozilla/gecko/home/CombinedHistoryPanel.java

@@ -17,6 +17,7 @@ import android.support.v4.app.LoaderManager;
 import android.support.v4.content.Loader;
 import android.support.v4.widget.SwipeRefreshLayout;
 import android.support.v7.widget.DefaultItemAnimator;
+import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.text.SpannableStringBuilder;
 import android.text.TextPaint;
@@ -146,11 +147,23 @@ public class CombinedHistoryPanel extends HomeFragment implements RemoteClientsD
         animator.setChangeDuration(100);
         animator.setMoveDuration(100);
         animator.setRemoveDuration(100);
+        mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
         mRecyclerView.setItemAnimator(animator);
         mRecyclerView.addItemDecoration(new DividerItemDecoration(getContext()));
         mRecyclerView.setOnHistoryClickedListener(mUrlOpenListener);
         mRecyclerView.setOnPanelLevelChangeListener(new OnLevelChangeListener());
         mRecyclerView.setHiddenClientsDialogBuilder(new HiddenClientsHelper());
+        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
+            @Override
+            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
+                super.onScrolled(recyclerView, dx, dy);
+                final LinearLayoutManager llm = (LinearLayoutManager) recyclerView.getLayoutManager();
+                if ((mPanelLevel == OnPanelLevelChangeListener.PanelLevel.PARENT) && (llm.findLastCompletelyVisibleItemPosition() == HistoryCursorLoader.HISTORY_LIMIT)) {
+                    Telemetry.sendUIEvent(TelemetryContract.Event.ACTION, TelemetryContract.Method.LIST, "history_scroll_max");
+                }
+
+            }
+        });
         registerForContextMenu(mRecyclerView);
     }
 
@@ -222,7 +235,7 @@ public class CombinedHistoryPanel extends HomeFragment implements RemoteClientsD
 
     private static class HistoryCursorLoader extends SimpleCursorLoader {
         // Max number of history results
-        private static final int HISTORY_LIMIT = 100;
+        public static final int HISTORY_LIMIT = 100;
         private final BrowserDB mDB;
 
         public HistoryCursorLoader(Context context) {