Support tracking focused element for OOPIFs.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index f928a0e9e749e76e9ceddd54174667c3475d7020..cc27ebebffe5286553e2a8d3967f198e70e328d8 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -793,9 +793,11 @@ void RenderWidgetHostViewAura::FocusedNodeTouched(
   ui::OnScreenKeyboardDisplayManager* osk_display_manager =
       ui::OnScreenKeyboardDisplayManager::GetInstance();
   DCHECK(osk_display_manager);
-  if (editable && host_ && host_->GetView()) {
+  if (editable && host_ && host_->GetView() && host_->delegate()) {
+    RenderWidgetHostImpl* host =
+        host_->delegate()->GetFocusedRenderWidgetHost(host_);
     keyboard_observer_.reset(new WinScreenKeyboardObserver(
-        host_, location_dips_screen, device_scale_factor_, window_));
+        host, location_dips_screen, device_scale_factor_, window_));

[ncarter (slow), 2016/12/16 19:17:21]

I'm thinking about the case here where (host_ != host), and the layering looks a
little odd.

Doesn't |host| have its own RWHView? It seems kind of strange for RWHVAura to
provide this service to other RWHs, and to have a |keyboard_observer_| member
that holds a pointer to the other |host|.

Among other things, I worry about:
 - what prevents the |host| pointer passed to WinScreenKeyboardObserver from
becoming invalid in the oopif case, if, say, it's an oopif widget whose FTN is
destroyed by a navigation?
 - When WinScreenKeyboardObserver calls SetInsets on |host|, and host is an
oopif widget, does the right thing happen? It seems like we want to adjust
insets on the outer RWHVAura, not the inner RWHVChildFrame.

[EhsanK, 2016/12/20 16:39:11]

Agreed. It is probably actually incorrect.
I think given that this is a page thing, RWHVAura should be a good place for
keeping keyboard reference. But |host| should not be that of a child frame.
Unfortunately nothing. If the RenderFrame goes out normally, we get a focused
node changed which will reset this. But I tested a case where I crashed the
renderer and this caused a browser crash.
I think (frome the comments in render_widget_host_view.h) this method should
only be called on page level view. So I should actually pass the old |host_|
instead of |host|.

But the scrolling for focused node will be broken and that needs extra fixes
that I am working on now. I left a comment above where the change should occur.

     virtual_keyboard_requested_ =
         osk_display_manager->DisplayVirtualKeyboard(keyboard_observer_.get());
   } else {