Update only unique references during rename refactoring.

editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java

Index: editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java
diff --git a/editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java b/editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java
index f791619b8be5432080e1d5c4dbeb5f4c7aa55640..83be2306f854b21f9a0886d6040b7bfee13f72f6 100644
--- a/editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java
+++ b/editor/tools/plugins/com.google.dart.engine.services/src/com/google/dart/engine/services/internal/refactoring/RenameRefactoringImpl.java
@@ -15,6 +15,8 @@
 package com.google.dart.engine.services.internal.refactoring;
 
 import com.google.common.base.Objects;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import com.google.dart.engine.element.Element;
 import com.google.dart.engine.element.LocalElement;
 import com.google.dart.engine.formatter.edit.Edit;
@@ -30,11 +32,13 @@ import com.google.dart.engine.utilities.source.SourceRange;
 
 import static com.google.dart.engine.utilities.source.SourceRangeFactory.rangeElementName;
 
+import java.util.List;
+import java.util.Set;
+
 /**
  * Abstract implementation of {@link RenameRefactoring}.
  */
 public abstract class RenameRefactoringImpl extends RefactoringImpl implements RenameRefactoring {
-
   /**
    * @return the {@link Edit} to replace the given {@link SearchMatch} reference.
    */
@@ -43,6 +47,19 @@ public abstract class RenameRefactoringImpl extends RefactoringImpl implements R
   }
 
   /**
+   * When one {@link Source} (one file) is used in more than one context, {@link SearchEngine} will
+   * return separate {@link SearchMatch} for each context. But in rename refactoring we want to
+   * update {@link Source} only once.
+   */
+  protected static List<SearchMatch> getUniqueMatches(List<SearchMatch> matches) {
+    Set<SearchMatch> uniqueMatches = Sets.newHashSet();
+    for (SearchMatch match : matches) {
+      uniqueMatches.add(match);
+    }
+    return Lists.newArrayList(uniqueMatches);
+  }
+
+  /**
    * @return {@code true} if two given {@link Element}s are {@link LocalElement}s and have
    *         intersecting with visibility ranges.
    */