Initial implementation of MemoryIndexStoreImpl and IndexContributor.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java
index 666a5aaed838a9cc75c25c0e71a00368f7142e6c..4a515aadab44bbfe54686a6b2f6624d2b4f403f6 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/Source.java
@@ -13,6 +13,8 @@
  */
 package com.google.dart.engine.source;
 
+import com.google.dart.engine.context.AnalysisContext;
+
 import java.nio.CharBuffer;
 
 /**
@@ -73,6 +75,11 @@ public interface Source {
   public String getFullName();
 
   /**
+   * @return the unique identifier for this source in its {@link AnalysisContext}.

[Brian Wilkerson, 2013/01/07 21:27:18]

This seems to imply that the unique identifier for a source could change from
context to context. Is that what you're thinking?

[scheglov, 2013/01/07 22:45:41]

I believe this comment is not correct.
I will remove getId() from Source for now.

+   */
+  public String getId();
+
+  /**
    * Return a short version of the name that can be displayed to the user to denote this source. For
    * example, for a source representing a file this would typically be the name of the file.
    *