Add support for 'display' in Manifest.

content/public/common/manifest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/common/manifest.h"
 
 namespace content {
 
 const size_t Manifest::kMaxIPCStringLength = 4 * 1024;
 
-Manifest::Manifest() {
+Manifest::Manifest()
+    : display(DISPLAY_MODE_UNSPECIFIED) {
 }
 
 Manifest::~Manifest() {
 }
 
 bool Manifest::IsEmpty() const {
-  return name.is_null() && short_name.is_null();
+  return name.is_null() &&
+         short_name.is_null() &&
+         start_url.is_empty() &&
+         display == DISPLAY_MODE_UNSPECIFIED;
 }
 
 } // namespace content