Adds routed interface support between RenderFrameHost and RenderFrame

content/public/browser/web_contents_frame_interface_binding.h

+// Copyright 2016 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_FRAME_INTERFACE_BINDING_H_
+#define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_FRAME_INTERFACE_BINDING_H_
+
+#include "base/macros.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_interface_registry.h"
+
+namespace content {
+
+// A scoper which binds |Interface| to |impl| for every RenderFrameHost
+// belonging to a single WebContents instance.
+template <typename Interface>
+class WebContentsFrameInterfaceBinding {
+ public:
+  explicit WebContentsFrameInterfaceBinding(Interface* impl)
+      : WebContentsFrameInterfaceBinding(nullptr, impl) {}
+
+  WebContentsFrameInterfaceBinding(WebContents* web_contents, Interface* impl)
+      : impl_(impl) {
+    if (web_contents)
+      AddToWebContents(web_contents);
+  }
+
+  ~WebContentsFrameInterfaceBinding() {
+    RemoveFromWebContents();
+  }
+
+  void AddToWebContents(WebContents* web_contents) {

[Sam McNally, 2016/09/09 05:33:15]

This could be clearer that an instance can be added to at most one WebContents.
Maybe SetWebContents()/ClearWebContents().

[Ken Rockot(use gerrit already), 2016/09/09 16:01:50]

Done

+    DCHECK(!weak_registry_);
+    WebContentsInterfaceRegistry* registry = web_contents->GetInterfaces();
+    registry->AddFrameInterface<Interface>(impl_);
+    weak_registry_ = registry->GetWeakPtr();
+  }
+
+  void RemoveFromWebContents() {
+    if (weak_registry_) {
+      weak_registry_->RemoveFrameInterface<Interface>();
+      weak_registry_.reset();
+    }
+  }

[Sam McNally, 2016/09/09 05:33:15]

Please add a current RenderFrameHost accessor. It should be able to pull it from
|weak_registry_|.

[Ken Rockot(use gerrit already), 2016/09/09 16:01:50]

Done

+
+ private:
+  Interface* impl_;
+
+  // We store a WeakPtr to the registry, because some
+  // WebBontentsFrameInterfaceBinding owners may exist as UserData on a
+  // WebContents and therefore outlive the WebContents itself.
+  base::WeakPtr<WebContentsInterfaceRegistry> weak_registry_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebContentsFrameInterfaceBinding);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_FRAME_INTERFACE_BINDING_H_