Add a NavigationThrottle to the public content/ interface

content/public/browser/navigation_handle.cc

Index: content/public/browser/navigation_handle.cc
diff --git a/content/public/browser/navigation_handle.cc b/content/public/browser/navigation_handle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..091a2ac624693ae1e2dac32bf0b6b377c271d0f2
--- /dev/null
+++ b/content/public/browser/navigation_handle.cc
@@ -0,0 +1,34 @@
+// 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 a it would be a

[Charlie Reis, 2015/09/18 05:40:02]

nit: s/a/as/

[clamy, 2015/09/18 17:35:39]

Done.

+  // 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)
+                              ->GetMainFrame()
+                              ->frame_tree_node()
+                              ->navigator()
+                              ->GetDelegate());

[nasko, 2015/09/17 21:10:25]

Uh, this is a fairly long chain. Why not use the RFH as input parameter? Also it
will work nicely if we wanted to do navigations in subframes.

[Charlie Reis, 2015/09/18 05:40:02]

I'm not sure we know the RFH at the time (e.g., in PlzNavigate).

That said, won't this expression always evaluate to |web_contents|, just like
the cast we're doing above?  Seems like we could just use that.

[clamy, 2015/09/18 17:35:39]

Done.

+  return scoped_ptr<NavigationHandle>(handle_impl.Pass());
+}
+
+}  // namespace content