Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/browser/browser_plugin/browser_plugin_guest.h

Index: content/browser/browser_plugin/browser_plugin_guest.h
diff --git a/content/browser/browser_plugin/browser_plugin_guest.h b/content/browser/browser_plugin/browser_plugin_guest.h
index 1705d009e573f51bfe91903b8dc35a0093b2ff08..e621ebaac521eab4fb449b9109f56ed4300c86b3 100644
--- a/content/browser/browser_plugin/browser_plugin_guest.h
+++ b/content/browser/browser_plugin/browser_plugin_guest.h
@@ -65,6 +65,7 @@ namespace content {
 class BrowserPluginGuestManager;
 class RenderViewHostImpl;
 class RenderWidgetHost;
+class RenderWidgetHostImpl;
 class RenderWidgetHostView;
 class RenderWidgetHostViewBase;
 class SiteInstance;
@@ -279,6 +280,9 @@ class CONTENT_EXPORT BrowserPluginGuest : public GuestHost,
  private:
   class EmbedderVisibilityObserver;
 
+  // The RenderWidgetHostImpl corresponding to the owner frame of BrowserPlugin.
+  RenderWidgetHostImpl* GetOwnerRenderWidgetHost() const;
+
   void InitInternal(const BrowserPluginHostMsg_Attach_Params& params,
                     WebContentsImpl* owner_web_contents);