Reland of Add a NavigationThrottle to the public content/ interface

content/public/browser/navigation_handle.cc

+// Copyright 2015 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/browser/navigation_handle.h"
+
+#include "content/browser/frame_host/navigation_handle_impl.h"
+#include "content/browser/frame_host/navigator.h"
+#include "content/browser/web_contents/web_contents_impl.h"
+
+namespace content {
+
+WebContents* NavigationHandle::GetWebContents() {
+  // The NavigationHandleImpl cannot access the WebContentsImpl as it would be
+  // a layering violation, hence the cast here.
+  return static_cast<WebContentsImpl*>(
+      static_cast<NavigationHandleImpl*>(this)->delegate());
+}
+
+// static
+scoped_ptr<NavigationHandle> NavigationHandle::CreateNavigationHandleForTesting(
+    const GURL& url,
+    bool is_main_frame,
+    WebContents* web_contents) {
+  scoped_ptr<NavigationHandleImpl> handle_impl = NavigationHandleImpl::Create(
+      url, is_main_frame, static_cast<WebContentsImpl*>(web_contents));
+  return scoped_ptr<NavigationHandle>(handle_impl.Pass());
+}
+
+}  // namespace content