Remove unnecessary 'virtual' annotation from mojo

mojo/services/html_viewer/webstoragenamespace_impl.cc

Index: mojo/services/html_viewer/webstoragenamespace_impl.cc
diff --git a/mojo/services/html_viewer/webstoragenamespace_impl.cc b/mojo/services/html_viewer/webstoragenamespace_impl.cc
index 12a5060f3d49e3b7aeccd65de4bc60bcb6f7eafe..47d79180f1adb14375e411e0b70d6084579bcb85 100644
--- a/mojo/services/html_viewer/webstoragenamespace_impl.cc
+++ b/mojo/services/html_viewer/webstoragenamespace_impl.cc
@@ -13,13 +13,9 @@ namespace {
 
 class DummyWebStorageAreaImpl : public blink::WebStorageArea {
  public:
-  virtual unsigned length() {
-    return 0;
-  }
-  virtual blink::WebString key(unsigned index) {
-    return blink::WebString();
-  }
-  virtual blink::WebString getItem(const blink::WebString& key) {
+  unsigned length() override { return 0; }
+  blink::WebString key(unsigned index) override { return blink::WebString(); }
+  blink::WebString getItem(const blink::WebString& key) override {
     return blink::WebString();
   }
 };