Puts JsScope on a diet

compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java

Index: compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java
diff --git a/compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java b/compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java
index 178f85e51f642519a25c80a142df8dd0b4c4abbf..d61cea78442573cb99bc61b64b07eaa21918cb7d 100644
--- a/compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java
+++ b/compiler/java/com/google/dart/compiler/backend/js/ast/JsScope.java
@@ -4,6 +4,8 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
+import com.google.common.collect.Interner;
+import com.google.common.collect.Interners;
 import com.google.dart.compiler.util.Lists;
 import com.google.dart.compiler.util.Maps;
 
@@ -43,25 +45,26 @@ public class JsScope implements Serializable {
 
   private List<JsScope> children = Collections.emptyList();
   private final String description;
-  private Map<String, JsName> names = Collections.emptyMap();
+  private Map<String, JsName> names; // Lazy init to save memory
   private JsScope parent;
   protected int tempIndex = 0;
   private final String scopeId;
+  private static Interner<String> interner = Interners.newWeakInterner();
 
- /* 
+ /*
   * Create a scope with parent.
   */
  public JsScope(JsScope parent, String description) {
    this(parent, description, null);
  }
- 
+
   /**
    * Create a scope with parent.
    */
   public JsScope(JsScope parent, String description, String scopeId) {
     assert (parent != null);
     this.scopeId = scopeId;
-    this.description = description;
+    this.description = interner.intern(description);
     this.parent = parent;
     parent.children = Lists.add(parent.children, this);
   }
@@ -241,8 +244,12 @@ public class JsScope implements Serializable {
   /**
    * Returns an iterator for all the names defined by this scope.
    */
+  @SuppressWarnings("unchecked")
   public Iterator<JsName> getAllNames() {
-    return names.values().iterator();
+    if (names != null) {
+      return names.values().iterator();
+    }
+    return Collections.EMPTY_LIST.iterator();
   }
 
   /**
@@ -282,6 +289,9 @@ public class JsScope implements Serializable {
    */
   protected JsName doCreateName(String ident, String shortIdent, String originalName) {
     JsName name = new JsName(this, ident, shortIdent, originalName);
+    if (names == null) {
+      names = Maps.create();
+    }
     names = Maps.putOrdered(names, ident, name);
     return name;
   }
@@ -293,6 +303,9 @@ public class JsScope implements Serializable {
    * @return <code>null</code> if the identifier has no associated name
    */
   protected JsName findExistingNameNoRecurse(String ident) {
-    return names.get(ident);
+    if (names != null) {
+      return names.get(ident);
+    }
+    return null;
   }
 }