Fix window.history.go() with no parameter.

ios/web/web_state/ui/crw_web_controller.mm

 // Copyright 2012 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.
 
 #import "ios/web/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #import <objc/runtime.h>
 #include <stddef.h>
@@ skipping 3066 matching lines @@
 }
 
 - (BOOL)handleWindowHistoryForwardMessage:(base::DictionaryValue*)message
                                   context:(NSDictionary*)context {
   [self goDelta:1];
   return YES;
 }
 
 - (BOOL)handleWindowHistoryGoMessage:(base::DictionaryValue*)message
                              context:(NSDictionary*)context {
+  std::string valueKey = "value";
+  if (!message->HasKey(valueKey)) {
+    // window.history.go() with no input parameter should behave as

[Eugene But (OOO till 7-30), 2016/12/09 22:58:19]

Should we fix this in JS as follows?:

|invokeOnHost_({'command': 'window.history.go', 'value': delta | 0});|

[kkhorimoto, 2016/12/13 00:30:56]

Done.

+    // window.history.go(0).
+    [self goDelta:0];
+    return YES;
+  }
   int delta = 0;
-  if (message->GetInteger("value", &delta)) {
+  if (message->GetInteger(valueKey, &delta)) {
     [self goDelta:delta];
     return YES;
   }
   return NO;
 }
 
 - (BOOL)handleWindowHistoryWillChangeStateMessage:(base::DictionaryValue*)unused
                                           context:(NSDictionary*)unusedContext {
   _changingHistoryState = YES;
   return YES;
@@ skipping 2693 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end