Initial implementation of MemoryIndexStoreImpl and IndexContributor.

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

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/FileBasedSource.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/FileBasedSource.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/FileBasedSource.java
index 634ef4c8c696a412925f269e136e05e251594a1d..7e17374022ab526ee306cd3f4b2acb66bd30d6ae 100644
--- a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/FileBasedSource.java
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/source/FileBasedSource.java
@@ -28,17 +28,17 @@ public class FileBasedSource implements Source {
    * The source factory that created this source and that should be used to resolve URI's against
    * this source.
    */
-  private SourceFactory factory;
+  private final SourceFactory factory;
 
   /**
    * The file represented by this source.
    */
-  private File file;
+  private final File file;
 
   /**
    * A flag indicating whether this source is in one of the system libraries.
    */
-  private boolean inSystemLibrary;
+  private final boolean inSystemLibrary;
 
   /**
    * The character set used to decode bytes into characters.
@@ -121,6 +121,12 @@ public class FileBasedSource implements Source {
   }
 
   @Override
+  public String getId() {

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

nit: I would much prefer getIdentifier. I don't like abbreviations :-)

+    // TODO(scheglov) use canonical path, but to get it we need to handle IOException

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

Unless we always use canonical paths (that is, the file's path is already
canonical), in which case we can just return the absolute path.

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

Do we need to return not-canonical File from FileBasedSource.getFile() because
we use it later to resolve relative URIs?

In any case, removed for now.

+    throw new UnsupportedOperationException();
+  }
+
+  @Override
   public String getShortName() {
     return file.getName();
   }