Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/public/browser/browser_plugin_guest_delegate.h

Index: content/public/browser/browser_plugin_guest_delegate.h
diff --git a/content/public/browser/browser_plugin_guest_delegate.h b/content/public/browser/browser_plugin_guest_delegate.h
index 0f805651ba8bafe5240a5fbe5772e06d43a75081..c6f3bc1cea88c4ddbefb762ede261dde7ed80508 100644
--- a/content/public/browser/browser_plugin_guest_delegate.h
+++ b/content/public/browser/browser_plugin_guest_delegate.h
@@ -97,6 +97,11 @@ class CONTENT_EXPORT BrowserPluginGuestDelegate {
   // a BrowserPlugin even when we are using cross process frames for guests. It
   // should be removed after resolving https://crbug.com/642826).
   virtual bool CanUseCrossProcessFrames();
+
+  // Returns the RenderFrameHost corresponding to the RenderFrame embedding the
+  // BrowserPlugin. This is the main frame for the owner of the guests, unless,

[nasko, 2016/10/27 21:03:40]

Based on the implementation, it returns the main frame of the embedder. A
GuestView can be embedded in arbitrary level of iframe nesting, right?

[EhsanK, 2016/10/27 22:06:48]

As far as I can tell, only MimeHandlerViewGuest can be embedded inside an
<iframe>. So for all other guest views, the way it is implemented now, will
return |owner_web_contents_->GetMainFrame()|.

[nasko, 2016/11/09 01:13:07]

I haven't had a chance to try it manually, but other than things not working
properly, it should be possible to use <webview> inside an <iframe> inside an
App v2.

[EhsanK, 2016/11/15 19:54:22]

You are right but I have not been able to do it inside an OOPIF. As long as the
<iframe> is in the same process as the main frame, we could as well assume the
main frame is the embedder, right?

+  // the guest is embedded inside a cross origin frame.

[nasko, 2016/10/27 21:03:40]

Can we have cross-origin frames in apps?

[EhsanK, 2016/10/27 22:06:48]

I don't think we can use <iframe>'s in apps at all. For external content we are
supposed to use <webview> there.

[nasko, 2016/11/09 01:13:07]

AFAIK, you can use <iframes> to local files in the crx of the app.

[EhsanK, 2016/11/15 19:54:22]

You are correct. I could do this using web_accessible_resources. But I could not
find a way to make the <iframe> cross origin. I talked to lazyboy@ and he also
agrees on "possibly no way to have guest inside OOPIF".

So in short, I guess we might be able to add the machinery to support it, but
there seems to be no apparent use case for it.

In case we intent to support guest in OOPIF for all guests, I can work in a
separate CL to avoid making this one too large. What do you suggest?

[Charlie Reis, 2016/11/15 23:45:32]

We don't need to support the more general case in this CL, but let's avoid the
frame-based API if we can.

+  virtual RenderFrameHost* GetEmbedderFrame();
 };
 
 }  // namespace content