Introduce WebRemoteFrameBase to break dependencies on WebRemoteFrameImpl.

third_party/WebKit/Source/core/frame/WebRemoteFrameBase.cpp

+// 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.
+
+#include "core/frame/WebRemoteFrameBase.h"
+
+#include "core/frame/RemoteFrame.h"
+#include "core/page/ChromeClient.h"
+#include "core/page/Page.h"
+
+namespace blink {
+
+WebRemoteFrameBase* WebRemoteFrameBase::FromFrame(RemoteFrame& frame) {
+  if (frame.GetPage()) {
+    return frame.GetPage()->GetChromeClient().GetWebRemoteFrameBase(frame);
+  }
+  return nullptr;
+}
+
+}  // namespace blink