Implement search for PrefixElement.

pkg/analyzer/lib/src/dart/analysis/search.dart

Index: pkg/analyzer/lib/src/dart/analysis/search.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/search.dart b/pkg/analyzer/lib/src/dart/analysis/search.dart
index 55d28d61cb6d8caa7fe709d7b7727e228aa1f38f..6cbc37a8cd0182a215c5fb350bb6b49f5023f2b9 100644
--- a/pkg/analyzer/lib/src/dart/analysis/search.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/search.dart
@@ -60,6 +60,8 @@ class Search {
       return _searchReferences_Local(element, (n) => n is Block);
     } else if (kind == ElementKind.PARAMETER) {
       return _searchReferences_Parameter(element);
+    } else if (kind == ElementKind.PREFIX) {
+      return _searchReferences_Prefix(element);
     } else if (kind == ElementKind.TYPE_PARAMETER) {
       return _searchReferences_Local(
           element, (n) => n.parent is CompilationUnit);
@@ -196,6 +198,21 @@ class Search {
     }));
     return results;
   }
+
+  Future<List<SearchResult>> _searchReferences_Prefix(
+      PrefixElement element) async {
+    List<SearchResult> results = <SearchResult>[];
+    LibraryElement libraryElement = element.library;
+    for (CompilationUnitElement unitElement in libraryElement.units) {
+      String unitPath = unitElement.source.fullName;
+      AnalysisResult unitAnalysisResult = await _driver.getResult(unitPath);
+      _LocalReferencesVisitor visitor =
+          new _LocalReferencesVisitor(element, unitElement);
+      unitAnalysisResult.unit.accept(visitor);
+      results.addAll(visitor.results);
+    }
+    return results;
+  }
 }
 
 /**