Create only a single LegacyRenderWidgetHostHWND per WebContentsViewAura.

content/browser/renderer_host/legacy_render_widget_host_win_delegate.h

Index: content/browser/renderer_host/legacy_render_widget_host_win_delegate.h
diff --git a/content/browser/renderer_host/legacy_render_widget_host_win_delegate.h b/content/browser/renderer_host/legacy_render_widget_host_win_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..92deeddb80d7c55457bce1ddd2cc777b4fcbb08a
--- /dev/null
+++ b/content/browser/renderer_host/legacy_render_widget_host_win_delegate.h
@@ -0,0 +1,26 @@
+// 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_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_DELEGATE_H_
+#define CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_DELEGATE_H_
+
+#include "content/common/content_export.h"
+#include "ui/gfx/native_widget_types.h"
+
+namespace content {
+
+// A delegate interface for LegacyRenderWidgetHostHWND to query the
+// native view accessible from the owner class.
+class CONTENT_EXPORT LegacyRenderWidgetHostHWNDDelegate {
+ public:
+  // Get the native view accessible for the web contents.
+  // Once initialized, this should always return a valid object, but the
+  // object may change as the user navigates.
+  virtual gfx::NativeViewAccessible GetNativeViewAccessible() = 0;
+};
+
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_DELEGATE_H_