Add history popup when long pressing on the back key.

content/public/android/java/src/org/chromium/content/browser/NavigationClient.java

Index: content/public/android/java/src/org/chromium/content/browser/NavigationClient.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/NavigationClient.java b/content/public/android/java/src/org/chromium/content/browser/NavigationClient.java
new file mode 100644
index 0000000000000000000000000000000000000000..505d48ec54e9f11919b7d86f519a311efafa06ec
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/NavigationClient.java
@@ -0,0 +1,26 @@
+// Copyright (c) 2013 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.
+
+package org.chromium.content.browser;
+
+/**
+ * Provides functionality needed to query and page history and the ability to access
+ * items in the history.
+ */
+public interface NavigationClient {
+
+    /**
+     * Get a directed copy of the navigation history of the view.
+     * @param isForward Whether the returned history should be entries after the current entry.
+     * @param itemLimit The limit on the number of items included in the history.
+     * @return A directed navigation for the page.
+     */
+    public NavigationHistory getDirectedNavigationHistory(boolean isForward, int itemLimit);
+
+    /**
+     * Navigates to the specified index in the navigation entry for this page.
+     * @param index The navigation index to navigate to.
+     */
+    public void goToNavigationIndex(int index);
+}