ahat: limit default number of results shown.

Previously, ahat had performance issues rendering large pages. This
change causes ahat to limit the number results shown in large pages by
default, requiring the user to explicitly request more information if
they care about it.

Bug: 25114227
Change-Id: Ief67396be254be4c84e6971f5b903a701206e17b
diff --git a/tools/ahat/src/ObjectsHandler.java b/tools/ahat/src/ObjectsHandler.java
index 4e9c42e..8ad3f48 100644
--- a/tools/ahat/src/ObjectsHandler.java
+++ b/tools/ahat/src/ObjectsHandler.java
@@ -22,9 +22,13 @@
 import java.util.Collections;
 import java.util.List;
 
-class ObjectsHandler extends AhatHandler {
+class ObjectsHandler implements AhatHandler {
+  private static final String OBJECTS_ID = "objects";
+
+  private AhatSnapshot mSnapshot;
+
   public ObjectsHandler(AhatSnapshot snapshot) {
-    super(snapshot);
+    mSnapshot = snapshot;
   }
 
   @Override
@@ -51,13 +55,15 @@
         new Column("Size", Column.Align.RIGHT),
         new Column("Heap"),
         new Column("Object"));
-    for (Instance inst : insts) {
+    SubsetSelector<Instance> selector = new SubsetSelector(query, OBJECTS_ID, insts);
+    for (Instance inst : selector.selected()) {
       doc.row(
           DocString.format("%,d", inst.getSize()),
           DocString.text(inst.getHeap().getName()),
           Value.render(inst));
     }
     doc.end();
+    selector.render(doc);
   }
 }