Backport B+ tree implementation from Dart to Java.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/InternalNodeData.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/InternalNodeData.java
diff --git a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/model/AnalysisServerOutlineListener.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/InternalNodeData.java
similarity index 60%
copy from editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/model/AnalysisServerOutlineListener.java
copy to editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/InternalNodeData.java
index 3f312fd65074cd0be87ec74d74e3f9af78e522ff..b9a5f15d3082c79c49af6595cd5acb562186c96a 100644
--- a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/model/AnalysisServerOutlineListener.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/InternalNodeData.java
@@ -11,19 +11,21 @@
  * or implied. See the License for the specific language governing permissions and limitations under
  * the License.
  */
+package com.google.dart.engine.internal.index.structure.btree;
 
-package com.google.dart.tools.core.analysis.model;
-
-import com.google.dart.server.Outline;
+import java.util.List;
 
 /**
- * Used by {@link AnalysisServerData} to notify clients that new {@link Outline} is ready.
+ * A container with information about an internal node.
  * 
- * @coverage dart.tools.core.model
+ * @coverage dart.engine.index.structure
  */
-public interface AnalysisServerOutlineListener {
-  /**
-   * Called when {@link Outline} for a particular file is ready.
-   */
-  void computedOutline(String file, Outline outline);
+public class InternalNodeData<K, N> {
+  public final List<K> keys;
+  public final List<N> children;
+
+  public InternalNodeData(List<K> keys, List<N> children) {
+    this.keys = keys;
+    this.children = children;
+  }
 }