Initial implementation of MemoryIndexStoreImpl and IndexContributor.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java
index 5b86c60b1f6ca2b677fa62393a56c076c153bc5f..cd2de29a0b33adb40d1c51a5aa45e4e6f0e1a02d 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/operation/IndexUnitOperation.java
@@ -22,8 +22,8 @@ import com.google.dart.engine.internal.index.IndexContributor;
 import com.google.dart.engine.source.Source;
 
 /**
- * Instances of the {@link IndexUnitOperation} implement an operation that adds data to the
- * index based on the content of a specified resource.
+ * Instances of the {@link IndexUnitOperation} implement an operation that adds data to the index
+ * based on the content of a specified resource.
  */
 public class IndexUnitOperation implements IndexOperation {
   /**
@@ -76,7 +76,7 @@ public class IndexUnitOperation implements IndexOperation {
   @Override
   public void performOperation() {
     synchronized (indexStore) {
-      indexStore.regenerateResource(source);
+      indexStore.removeSource(source);
       try {
         IndexContributor contributor = new IndexContributor(indexStore);
         unit.accept(contributor);