<webview>: Move back, forward, canGoBack, canGoForward, go from content to chrome

chrome/browser/webview/webview_constants.cc

 // Copyright 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.
 
 #include "chrome/browser/webview/webview_constants.h"
 
 namespace webview {
 
 // Events.
 const char kEventLoadCommit[] = "webview.onLoadCommit";
 
 // Parameters/properties on events.
 const char kIsTopLevel[] = "isTopLevel";
 const char kUrl[] = "url";
 
+// Internal parameters/properties on events.
+const char kInternalCurrentEntryIndex[] = "currentEntryIndex";
+const char kInternalEntryCount[] = "entryCount";
+
 // Attributes.
 const char kAttributeApi[] = "api";
 
 }  // namespace webview