Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/browser/browser_plugin/browser_plugin_guest.cc

Index: content/browser/browser_plugin/browser_plugin_guest.cc
diff --git a/content/browser/browser_plugin/browser_plugin_guest.cc b/content/browser/browser_plugin/browser_plugin_guest.cc
index 461081dc723d4c338a3248725dc4a7e8e8bcdde1..26009cdffd0a1d7725f5f76492d4d17dc82fef29 100644
--- a/content/browser/browser_plugin/browser_plugin_guest.cc
+++ b/content/browser/browser_plugin/browser_plugin_guest.cc
@@ -136,10 +136,12 @@ int BrowserPluginGuest::GetGuestProxyRoutingID() {
   // owners in different processes. We probably need to clear the
   // |guest_proxy_routing_id_| and perform any necessary cleanup on Detach
   // to enable this.
-  SiteInstance* owner_site_instance = owner_web_contents_->GetSiteInstance();
-  int proxy_routing_id =
-      GetWebContents()->GetFrameTree()->root()->render_manager()->
-          CreateRenderFrameProxy(owner_site_instance);
+  SiteInstance* owner_site_instance = GetEmbedderFrame()->GetSiteInstance();
+  int proxy_routing_id = GetWebContents()
+                             ->GetFrameTree()
+                             ->root()
+                             ->render_manager()
+                             ->CreateRenderFrameProxy(owner_site_instance);

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

This doesn't seem right, as we take the SiteInstance from the frame, which might
not be the root, yet we create the proxy in the root frame. Shouldn't this be
GetEmbedderFrame()->frame_tree_node()->render_manager()->CreateRenderFrameProxy()?

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

This was my main question from you on this CL. Thanks for bringing it up!

This is what I understand so far:

1- We do create the RFPH in the root, but it is the root of the guest frame
tree. This way the RFP in the embedder frame's process can be used to post
message to the guest.
2- This would technically create the reverse path for post messaging, i.e., RFP
in guest process to message back (right?). However, calling this on the a frame
tree node which is not root and does not have a RenderViewHostImpl yet, will
cause a browser crash through CHECK:
https://cs.chromium.org/chromium/src/content/browser/frame_host/render_frame_...

So my question is, a) Is it OK to create RFPH in the node which is not main
frame given the context here: https://crbug.com/485520 and b) if yes, then how
can I do it? is it OK to remove the CHECK above?

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

I didn't realize at the time that GetEmbedderFrame() and GetWebContents() come
from two different frame trees. I think what you have is correct -
GetWebContents() will return the guest one, which needs a proxy in the embedder
process for it. So using the SiteInstance of the embedder frame is correct.

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

Acknowledged.

   guest_proxy_routing_id_ = RenderFrameProxyHost::FromID(
       owner_site_instance->GetProcess()->GetID(), proxy_routing_id)
           ->GetRenderViewHost()->GetRoutingID();
@@ -170,6 +172,10 @@ void BrowserPluginGuest::WillDestroy() {
   attached_ = false;
 }
 
+RenderFrameHostImpl* BrowserPluginGuest::GetEmbedderFrame() const {
+  return static_cast<RenderFrameHostImpl*>(delegate_->GetEmbedderFrame());
+}
+
 void BrowserPluginGuest::Init() {
   if (initialized_)
     return;
@@ -242,11 +248,10 @@ bool BrowserPluginGuest::OnMessageReceivedFromEmbedder(
   RenderWidgetHostViewGuest* rwhv = static_cast<RenderWidgetHostViewGuest*>(
       web_contents()->GetRenderWidgetHostView());
   // Until the guest is attached, it should not be handling input events.
-  if (attached() && rwhv &&
-      rwhv->OnMessageReceivedFromEmbedder(
-          message,
-          RenderWidgetHostImpl::From(
-              embedder_web_contents()->GetRenderViewHost()->GetWidget()))) {
+  RenderFrameHostImpl* rfhi = GetEmbedderFrame();
+  RenderWidgetHostImpl* rwhi = rfhi ? rfhi->GetRenderWidgetHost() : nullptr;
+  if (attached() && rwhv && rwhi &&
+      rwhv->OnMessageReceivedFromEmbedder(message, rwhi)) {
     return true;
   }
 
@@ -374,9 +379,10 @@ bool BrowserPluginGuest::IsGuest(RenderViewHostImpl* render_view_host) {
 }
 
 RenderWidgetHostView* BrowserPluginGuest::GetOwnerRenderWidgetHostView() {
-  if (!owner_web_contents_)
-    return nullptr;
-  return owner_web_contents_->GetRenderWidgetHostView();
+  if (GetEmbedderFrame())
+    return GetEmbedderFrame()->GetView();
+
+  return nullptr;
 }
 
 void BrowserPluginGuest::UpdateVisibility() {
@@ -448,8 +454,8 @@ void BrowserPluginGuest::ResendEventToEmbedder(
     return;
 
   DCHECK(browser_plugin_instance_id_);
-  RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
-      embedder_web_contents()->GetMainFrame()->GetView());
+  RenderWidgetHostViewBase* view =
+      static_cast<RenderWidgetHostViewBase*>(GetOwnerRenderWidgetHostView());
 
   gfx::Vector2d offset_from_embedder = guest_window_rect_.OffsetFromOrigin();
   if (event.type == blink::WebInputEvent::GestureScrollUpdate) {
@@ -506,7 +512,8 @@ void BrowserPluginGuest::SendMessageToEmbedder(
     pending_messages_.push_back(std::move(msg));
     return;
   }
-  owner_web_contents_->Send(msg.release());
+
+  GetEmbedderFrame()->GetRenderWidgetHost()->Send(msg.release());
 }
 
 void BrowserPluginGuest::DragSourceEndedAt(int client_x, int client_y,