Simplifies the structure of app_list search a bit.

ash/shell/app_list.cc

Index: ash/shell/app_list.cc
diff --git a/ash/shell/app_list.cc b/ash/shell/app_list.cc
index 2f725e2b1bf73adcbfa823440e069b77cc8bdab2..77d65ef2428dd5e7fdb2b9c09a379a03d260b329 100644
--- a/ash/shell/app_list.cc
+++ b/ash/shell/app_list.cc
@@ -188,6 +188,11 @@ class ExampleSearchResult : public app_list::SearchResult {
 
   WindowTypeShelfItem::Type type() const { return type_; }
 
+  // app_list::SearchResult:
+  virtual scoped_ptr<SearchResult> Duplicate() override {
+    return scoped_ptr<SearchResult>();
+  }
+
  private:
   WindowTypeShelfItem::Type type_;