[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/navigation/web_view_navigation_proxy_impl.mm

+// Copyright 2017 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 <WebKit/WebKit.h>
+#include "base/logging.h"
+
+#include "ios/web/navigation/web_view_navigation_proxy_impl.h"
+
+namespace web {
+
+WebViewNavigationProxyImpl::WebViewNavigationProxyImpl(WKWebView* web_view)
+    : web_view_(web_view) {}
+
+bool WebViewNavigationProxyImpl::HasWebView() const {
+  return web_view_ != nullptr;
+}
+
+bool WebViewNavigationProxyImpl::CanGoBack() const {
+  return web_view_ && [web_view_ canGoBack];
+}
+
+bool WebViewNavigationProxyImpl::CanGoForward() const {
+  return web_view_ && [web_view_ canGoForward];
+}
+
+void WebViewNavigationProxyImpl::GoBack() const {
+  if (web_view_) {
+    [web_view_ goBack];
+  }
+}
+
+void WebViewNavigationProxyImpl::GoForward() const {
+  if (web_view_) {
+    [web_view_ goForward];
+  }
+}
+
+void WebViewNavigationProxyImpl::GoToBackForwardListItem(
+    WKBackForwardListItem* item) const {
+  if (web_view_) {
+    [web_view_ goToBackForwardListItem:item];
+  }
+}
+
+WKBackForwardListItem* WebViewNavigationProxyImpl::GetCurrentItem() const {
+  if (web_view_) {
+    return web_view_.backForwardList.currentItem;

[Eugene But (OOO till 7-30), 2017/06/27 22:02:00]

nit: No need for |if (web_view_) {| check. it's ok to call methods on nil. They
will return nil.

Same comment for other places where |web_view_| nil check is unnecessary.

[danyao, 2017/06/28 22:11:04]

Done.

+  } else {
+    return nullptr;
+  }
+}
+
+NSArray<WKBackForwardListItem*>* WebViewNavigationProxyImpl::GetBackList()
+    const {
+  DCHECK(web_view_);
+  return web_view_.backForwardList.backList;
+}
+
+NSArray<WKBackForwardListItem*>* WebViewNavigationProxyImpl::GetForwardList()
+    const {
+  DCHECK(web_view_);
+  return web_view_.backForwardList.forwardList;
+}
+
+WKBackForwardListItem* WebViewNavigationProxyImpl::GetItemAtOffset(
+    int offset) const {
+  DCHECK(web_view_);
+  return [web_view_.backForwardList itemAtIndex:offset];
+}
+
+void WebViewNavigationProxyImpl::SetWebView(WKWebView* web_view) {
+  web_view_ = web_view;
+}
+
+}  // namespace web